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Oterino, J., G. Sánchez Toranzo, L. Zelarayán, M. T. Ajmat, F. Bonilla y M. I. Bühler. "Behaviour of the vitelline envelope in Bufo arenarum oocytes matured in vitro in blockade to polyspermy". Zygote 14, n.º 2 (mayo de 2006): 97–106. http://dx.doi.org/10.1017/s0967199406003662.
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SummaryDuring activation of amphibian eggs, cortical granule exocytosis causes elaborate ultrastructural changes in the vitelline envelope. These changes involve modifications in the structure of the vitelline envelope and formation of a fertilization envelope (FE) that can no longer be penetrated by sperm. In Bufo arenarum, as the egg traverses the oviduct, the vitelline envelope is altered by a trypsin-like protease secreted by the oviduct, which induces an increased susceptibility of the vitelline envelope to sperm lysins. Full-grown oocytes of B. arenarum, matured in vitro by progesterone, are polyspermic, although cortical granule exocytosis seems to occur within a normal chronological sequence. These oocytes can be fertilized with or without trypsin treatment, suggesting that the vitelline envelope is totally sperm-permeable. Vitelline envelopes without trypsin treatment cannot retain either gp90 or gp96. This suggests that these glycoproteins are involved in the block to polyspermy and that trypsin treatment of matured in vitro oocytes before insemination is necessary to enable vitelline envelopes to block polyspermy. The loss of the binding capacity in vitelline envelopes isolated from B. arenarum oocytes matured in vitro with trypsin treatment and activated by electric shock suggests that previous trypsin treatment is a necessary step for sperm block to occur. When in vitro matured oocytes were incubated with the product of cortical granules obtained from in vitro matured oocytes (vCGP), vitelline envelopes with trypsin treatment were able to block sperm entry. These oocytes exhibited the characteristic signs of activation. These results support the idea that B. arenarum oocytes can be activated by external stimuli and suggest the presence of unknown oocyte surface receptors linked to the activation machinery in response to fertilization. Electrophoretic profiles obtained by SDS-PAGE of solubilized vitelline envelopes from oocytes matured in vitro revealed the conversion of gp40 (in vitro matured oocytes, without trypsin treatment) to gp38 (ascribable to trypsin activity or cortical granule product activity, CGP) and the conversion of gp70 to gp68 (ascribable to trypsin activity plus CGP activity). Taking into account that only the vitelline envelopes of in vitro matured oocytes with trypsin treatment and activated can block sperm entry, we may suggest that the conversion of gp70 to gp68 is related to the changes associated with sperm binding.
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Siebrasse, Jan Peter, Elias Coutavas y Reiner Peters. "Reconstitution of nuclear protein export in isolated nuclear envelopes". Journal of Cell Biology 158, n.º 5 (26 de agosto de 2002): 849–54. http://dx.doi.org/10.1083/jcb.200201130.
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Signal-dependent nuclear protein export was studied in perforated nuclei and isolated nuclear envelopes of Xenopus oocytes by optical single transporter recording. Manually isolated and purified oocyte nuclei were attached to isoporous filters and made permeable for macromolecules by perforation. Export of a recombinant protein (GG-NES) containing the nuclear export signal (NES) of the protein kinase A inhibitor through nuclear envelope patches spanning filter pores could be induced by the addition of GTP alone. Export continued against a concentration gradient, and was NES dependent and inhibited by leptomycin B and GTPγS, a nonhydrolyzable GTP analogue. Addition of recombinant RanBP3, a potential cofactor of CRM1-dependent export, did not promote GG-NES export at stoichiometric concentration but gradually inhibited export at higher concentrations. In isolated filter-attached nuclear envelopes, export of GG-NES was virtually abolished in the presence of GTP alone. However, a preformed export complex consisting of GG-NES, recombinant human CRM1, and RanGTP was rapidly exported. Unexpectedly, export was strongly reduced when the export complex contained RanGTPγS or RanG19V/Q69L-GTP, a GTPase-deficient Ran mutant. This paper shows that nuclear transport, previously studied in intact and permeabilized cells only, can be quantitatively analyzed in perforated nuclei and isolated nuclear envelopes.
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Cardoso, Vitor E. M., Pedro F. Pereira, Nuno M. M. Ramos y Ricardo M. S. F. Almeida. "The Impacts of Air Leakage Paths and Airtightness Levels on Air Change Rates". Buildings 10, n.º 3 (12 de marzo de 2020): 55. http://dx.doi.org/10.3390/buildings10030055.
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Southern European countries have milder climatic conditions that differ from their colder northern counterparts, which greatly influence indoor ventilation strategies. The relation between a building’s airtightness and the air change rates remains a topic to be fully tackled in these countries, since natural ventilation is very frequent. In this work, the ventilation and airtightness of a case study were analyzed in-depth to support a discussion on this topic. CO2 concentration decay and blower-door measurements were used to characterize the infiltration and ventilation conditions of the case study. The case study represents a common Portuguese situation, with highly permeable envelopes, combined with highly variable air change rates. Transient simulations were carried out for the comparison of scenarios where different configurations of possible air paths were analyzed. The simulations included both natural and mechanical ventilation scenarios. An air sweeping effect from bedroom to bathroom only occurred when the mechanical extraction ventilation (MEV) was on. Different air leakage path configurations resulted in substantial offsets, up to 63%, of the air change rate (ACH) due to natural occurring forces. The results confirmed that the relation between airtightness and air change rates should be carefully analyzed in southern European countries, as indoor air quality, comfort of occupants, and energy efficiency are highly influenced by the considered variables.
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Islam, MS, T. Akhter y M. Matsumoto. "Asterosap, an Egg Jelly Peptide, Elevate Intracellular Ca2+ and Activate the Motility of Spermatozoa". Progressive Agriculture 19, n.º 1 (18 de diciembre de 2013): 79–88. http://dx.doi.org/10.3329/pa.v19i1.17358.
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Components from the outer envelopes of the egg that influence the flagellar beating and acrosome reaction of spermatozoa are regulated by ion flux across the plasma membrane. Asterosap, a sperm-activating peptide from the starfish egg jelly layer, causes a transient increase in intracellular cyclic GMP (cGMP) through the activation of the asterosap receptor, a guanylyl cyclase (GC), and causes an increase in intracellular Ca2+. Here we describe the pathway of asterosap-induced Ca2+ elevation using different Ca2+ channel antagonists. Fluo-4 AM, a cell permeable Ca2+ sensitive dye was used to determine the channel caused by the asterosap-induced Ca2+ elevation in spermatozoa. Different L-type Ca2+ channel antagonists, a non specific Ca2+ channel antagonist (nickel chloride), and a store-operated Ca2+ channel (SOC) antagonist do not show any significant response on asterosap-induced Ca2+ elevation, whereas KB-R7943, a selective inhibitor against Na+/Ca2+ exchanger (NCX) inhibited effectively. We also analyzed the flagellar movement of spermatozoa in artificial seawater (ASW) containing the asterosap at 100 nM ml?1. We found that spermatozoa swam vigorously with more symmetrical flagellar movement in asterosap than in ASW and KB-R7943 significantly inhibited the flagellar movement.DOI: http://dx.doi.org/10.3329/pa.v19i1.17358 Progress. Agric. 19(1): 79 - 88, 2008
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Hussain, Atif y Pierre Blanchet. "Preparation of Breathable Cellulose Based Polymeric Membranes with Enhanced Water Resistance for the Building Industry". Materials 14, n.º 15 (1 de agosto de 2021): 4310. http://dx.doi.org/10.3390/ma14154310.
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This study focuses on the development of advanced water-resistant bio-based membranes with enhanced vapour permeability for use within building envelopes. Building walls are vulnerable to moisture damage and mold growth due to water penetration, built-in moisture, and interstitial condensation. In this work, breathable composite membranes were prepared using micro-fibrillated cellulose fiber (CF) and polylactic acid (PLA). The chemical composition and physical structure of CF is responsible for its hydrophilic nature, which affects its compatibility with polymers and consequently its performance in the presence of excessive moisture conditions. To enhance the dispersibility of CF in the PLA polymer, the fibers were treated with an organic phosphoric acid ester-based surfactant. The hygroscopic properties of the PLA-CF composites were improved after surfactant treatment and the membranes were resistant to water yet permeable to vapor. Morphological examination of the surface showed better interfacial adhesion and enhanced dispersion of CF in the PLA matrix. Thermal analysis revealed that the surfactant treatment of CF enhanced the glass transition temperature and thermal stability of the composite samples. These bio-based membranes have immense potential as durable, eco-friendly, weather resistant barriers for the building industry as they can adapt to varying humidity conditions, thus allowing entrapped water vapor to pass through and escape the building, eventually prolonging the building life.
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Goldberg, M. y D. Septier. "Phospholipids in Amelogenesis and Dentinogenesis". Critical Reviews in Oral Biology & Medicine 13, n.º 3 (mayo de 2002): 276–90. http://dx.doi.org/10.1177/154411130201300305.
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Phospholipids have been identified in enamel and dentin. Before demineralization, a group of phospholipids extracted by lipid solvents was associated with cell membranes and is therefore closely related to cell growth and intracellular regulations. After demineralization, a second group of phospholipids, associated with the extracellular matrix, was extracted; this group is probably linked to the mineralized phase. Using imidazole-osmium tetroxide fixation of rat incisors, we stained cellular unsaturated fatty acids, so that we could visualize the membrane domains, coated pits, and endocytic inclusions. Filipin, a probe for cholesterol, varied in density along the plasma membrane of secretory ameloblasts, and allowed us to visualize membrane remnants inside the forming enamel. With respect to phospholipids located in the extracellular matrix, the malachite-green–glutaraldehyde (MGA) method or iodoplatinate (IP) reaction retains and visualizes enamel and dentin phospholipids. In predentin, aggregates appearing as granules and filaments, or liposome-like structures, were located in the spaces between collagen fibrils. In dentin, organic envelopes coating the crystals, also named “crystal-ghost” structures, outlined groups of collagen fibrils. Histochemical data provided evidence that phospholipids are co-distributed or interact with proteoglycans. Radioautography after IP reaction established that [3H] choline was detected in dentin as early as 30 min after the intravenous injection of the labeled precursor, before any labeling was seen in odontoblasts and predentin. This suggests that blood-serum-labeled phospholipids pass between odontoblasts, cross the distal permeable junctional complex, and diffuse in dentin prior to any cellular uptake and phospholipid synthesis. Pharmacologically and genetically induced pathology also supports the suggestion that phospholipids play an important role in the formation and mineralization of dental tissues.
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EHRENMARK, ULF T. "On the normal incidence of linear waves over a plane incline partially covered by a rigid lid". Journal of Fluid Mechanics 623 (6 de marzo de 2009): 209–40. http://dx.doi.org/10.1017/s0022112008005296.
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The effect is examined on infinitesimal standing waves over a plane beach when restricted by the arbitrary placing of a finite rigid (or permeable) lid of length ℓ on the undisturbed surface. A uniformly bounded solution for the potential function is obtained by a Green's function method. The Green's function is derived and manipulated, for subsequent computational expedience, from a previously known solution for the problem of an oscillating line source placed at an arbitrary location in the sector. Applications are made to both the case of plate anchored at the origin and the case of plate anchored some distance at sea (drifted plate problem). In both cases water column potentials and equipotentials are constructed from the numerical solution of a Fredholm equation of the second kind by finite difference discretization. Solutions are further extended to include the logarithmically singular standing wave, combination with which allows the construction of progressing waves. Computation of initially incoming progressing wave envelopes demonstrates the emergence of a partially standing wave pattern shoreward of the plate. There is no difficulty, in principle, to extend the theory to any number of plates, and this is verified by computation for the case of two plates. A new shoreline radiation condition is constructed to allow formulation, in the usual way, of the reflection/transmission problem for the plate, and results are in good qualitative agreement with a similar model on a horizontal plane bed. It is argued that the Green's function constructed here could be used in a number of diverse problems, of this linear nature, where all, or part, of the submerged boundary is that of a plane incline.
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Brits, G. J. y J. C. Manning. "Seed structure and physiology in relation to recruitment ecology in Leucospermum (Proteaceae) in fynbos". Australian Journal of Botany 67, n.º 4 (2019): 290. http://dx.doi.org/10.1071/bt18199.
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Development of embryo envelopes in Leucospermum cordifolium (Salisb. ex Knight) Fourcade is presented in a detailed anatomical study, and their structure interpreted ecologically. To support interpretation results for at least six other species of Leucospermum are reviewed, confirming that L. cordifolium is representative of this shrubby group occurring in fynbos, a fire-prone Mediterranean-type vegetation subject to summer drought. The fate of the water-permeable seed coverings subsequent to dispersal is followed in seeds stored experimentally underground. The testa at maturity effectively excludes oxygen in intact soil-stored seeds, thus creating a less common type of physical dormancy which we term ‘anoxia PY’ (oxygen-impermeable physical dormancy). We postulate ‘fire-mediated desiccation-scarification’ testa breakage on a large scale in freshly dispersed (by ants) soil-stored young-seeds, dynamically regulated by drying of different testa layers through fire heat shock (but also by post-fire ambient climate heat), thus alleviating anoxia PY in, and causing undelayed germination of, a major part of the young-seed bank within the ensuing winter germination season. Concurrently a patchy disturbance pattern within a lesser portion of the young-seed cohort causes uneven underground desiccation-scarification by fire, resulting in variable degrees of oxygenation and thus temporally extended (erratic) germination of young-seeds. Both of these strategies are primary long term fitness traits in Leucospermum. By contrast the persistent older-seed cohort, stored underground during the inter-fire period, may become weathered by soil and climate factors (‘soil-mediated abrasion’), which alleviates anoxia PY in old seeds. Thermodormancy of these embryos (physiological dormancy, PD) is enforced in unburnt vegetation by two narrow habitat-dependent daily temperature requirements (~10°C × 20°C), and these have specific ecological functions. The complex Leucospermum system includes balanced adaptive responses to multiple selective pressures. We propose a coherent mechanistic profile for this fynbos genus, synthesising data partly from the literature of other fire-prone ecosystems.
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Koschinski, Andreas, Gerd Wengler, Gisela Wengler y Holger Repp. "Rare earth ions block the ion pores generated by the class II fusion proteins of alphaviruses and allow analysis of the biological functions of these pores". Journal of General Virology 86, n.º 12 (1 de diciembre de 2005): 3311–20. http://dx.doi.org/10.1099/vir.0.81096-0.
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Recently, class II fusion proteins have been identified on the surface of alpha- and flaviviruses. These proteins have two functions besides membrane fusion: they generate an isometric lattice on the viral surface and they form ion-permeable pores at low pH. An attempt was made to identify inhibitors for the ion pores generated by the fusion proteins of the alphaviruses Semliki Forest virus and Sindbis virus. These pores can be detected and analysed in three situations: (i) in the target membrane during virus entry, by performing patch-clamp measurements of membrane currents; (ii) in the virus particle, by studying the entry of propidium iodide; and (iii) in the plasma membrane of infected cells, by Fura-2 fluorescence imaging of Ca2+ entry into infected cells. It is shown here that, at a concentration of 0·1 mM, rare earth ions block the ion permeability of alphavirus ion pores in all three situations. Even at a concentration of 0·5 mM, these ions do not block formation of the viral fusion pore, as they do not inhibit entry or multiplication of alphaviruses. The data indicate that ions flow through the ion pores into the virus particle in the endosome and from the endosome into the cytoplasm after fusion of the viral envelope with the endosomal membrane. These ion flows, however, are not necessary for productive infection. The possibility that the ability of class II fusion proteins to form ion-permeable pores reflects their origin from protein toxins that form ion-permeable pores, and that entry via class II fusion proteins may resemble the entry of non-enveloped viruses, is discussed.
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Daugelavičius, Rimantas, Elena Bakiene˙ y Dennis H. Bamford. "Stages of Polymyxin B Interaction with theEscherichia coli Cell Envelope". Antimicrobial Agents and Chemotherapy 44, n.º 11 (1 de noviembre de 2000): 2969–78. http://dx.doi.org/10.1128/aac.44.11.2969-2978.2000.
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ABSTRACT The effects of polymyxin B (PMB) on the Escherichia coli outer (OM) and cytoplasmic membrane (CM) permeabilities were studied by monitoring the fluxes of tetraphenylphosphonium, phenyldicarbaundecaborane, and K+ and H+ions. At concentrations between 2 and 20 μg/ml, PMB increased the OM permeability to lipophilic compounds and induced a leakage of K+ from the cytosol and an accumulation of lipophilic anions in the cellular membranes but did not cause the depolarization of the CM. At higher concentrations, PMB depolarized the CM, forming ion-permeable pores in the cell envelope. The permeability characteristics of PMB-induced pores mimic those of bacteriophage- and/or bacteriocin-induced channels. However, the bactericidal effect of PMB took place at concentrations below 20 μg/ml, indicating that this effect is not caused by pore formation. Under conditions of increased ionic strength, PMB made the OM permeable to lipophilic compounds and decreased the K+gradient but was not able to depolarize the cells. The OM-permeabilizing effect of PMB can be diminished by increasing the concentration of Mg2+. The major new findings of this work are as follows: (i) the OM-permeabilizing action of PMB was dissected from its depolarizing effect on the CM, (ii) the PMB-induced ion-permeable pores in bacterial envelope were registered, and (iii) the pore formation and depolarization of the CM are not obligatory for the bactericidal action of PMB and dissipation of the K+gradient on the CM.
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Salina, Davide, Khaldon Bodoor, Paul Enarson, Wahyu Hendrati Raharjo y Brian Burke. "Nuclear envelope dynamics". Biochemistry and Cell Biology 79, n.º 5 (1 de octubre de 2001): 533–42. http://dx.doi.org/10.1139/o01-130.
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The nuclear envelope (NE) provides a semi permeable barrier between the nucleus and cytoplasm and plays a central role in the regulation of macromolecular trafficking between these two compartments. In addition to this transport function, the NE is a key determinant of interphase nuclear architecture. Defects in NE proteins such as A-type lamins and the inner nuclear membrane protein, emerin, result in several human diseases that include cardiac and skeletal myopathies as well as lipodystrophy. Certain disease-linked A-type lamin defects cause profound changes in nuclear organization such as loss of peripheral heterochromatin and redistribution of other nuclear envelope components. While clearly essential in maintenance of nuclear integrity, the NE is a highly dynamic organelle. In interphase it is constantly remodeled to accommodate nuclear growth. During mitosis it must be completely dispersed so that the condensed chromosomes may gain access to the mitotic spindle. Upon completion of mitosis, dispersed NE components are reutilized in the assembly of nuclei within each daughter cell. These complex NE rearrangements are under precise temporal and spatial control and involve interactions with microtubules, chromatin, and a variety of cell-cycle regulatory molecules.Key words: nuclear envelope, lamin, nuclear pore complex, nuclear membranes, mitosis.
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Brunetti, P., G. Basta, A. Faloerni, F. Calcinaro, M. Pietropaolo y R. Calafiore. "Immunoprotection of Pancreatic Islet Grafts within Artificial Microcapsules". International Journal of Artificial Organs 14, n.º 12 (diciembre de 1991): 789–91. http://dx.doi.org/10.1177/039139889101401208.
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To circumvent pancreatic islet graft-directed immune destruction we enveloped porcine islets within highly biocompatible and selectively permeable algin/polyaminoacid microcapsules. These special microspheres were deposited between the inner (permeable) and the outer (impermeable) layers of an artificial, coaxial vascular prosthesis, directly anastomized to blood vessels. Five dogs with spontaneous, insulin-dependent diabetes received microencapsulated porcine islets in arterio-vein iliac prosthesis by-passes. One showed complete and the remainder partial, sustained reversal of hyperglycemia. Microencapsulation may be a potential solution to immunological problems related to islet transplantation.
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Rost, Sylvia, Claudia Frank y Erwin Beck. "The chloroplast envelope is permeable for maltose but not for maltodextrins". Biochimica et Biophysica Acta (BBA) - General Subjects 1291, n.º 3 (diciembre de 1996): 221–27. http://dx.doi.org/10.1016/s0304-4165(96)00068-2.
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Steenhuis, Maurice, Corinne M. ten Hagen-Jongman, Peter van Ulsen y Joen Luirink. "Stress-Based High-Throughput Screening Assays to Identify Inhibitors of Cell Envelope Biogenesis". Antibiotics 9, n.º 11 (13 de noviembre de 2020): 808. http://dx.doi.org/10.3390/antibiotics9110808.
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The structural integrity of the Gram-negative cell envelope is guarded by several stress responses, such as the σE, Cpx and Rcs systems. Here, we report on assays that monitor these responses in E. coli upon addition of antibacterial compounds. Interestingly, compromised peptidoglycan synthesis, outer membrane biogenesis and LPS integrity predominantly activated the Rcs response, which we developed into a robust HTS (high-throughput screening) assay that is suited for phenotypic compound screening. Furthermore, by interrogating all three cell envelope stress reporters, and a reporter for the cytosolic heat-shock response as control, we found that inhibitors of specific envelope targets induce stress reporter profiles that are distinct in quality, amplitude and kinetics. Finally, we show that by using a host strain with a more permeable outer membrane, large-scaffold antibiotics can also be identified by the reporter assays. Together, the data suggest that stress profiling is a useful first filter for HTS aimed at inhibitors of cell envelope processes.
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Simonson, Carey J., Tuomo Ojanen y Mikael Salonvaara. "Moisture Performance of an Airtight, Vapor-permeable Building Envelope in a Cold Climate". Journal of Thermal Envelope and Building Science 28, n.º 3 (enero de 2005): 205–26. http://dx.doi.org/10.1177/1097196305048628.
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Zhang, Juan, Zhao Feng Chen, Jie Ming Zhou, Bin Bin Li y Zhou Chen. "A Novel Rigid Vacuum Insulation Panel: Vacuum Insulation Sandwich". Advanced Materials Research 430-432 (enero de 2012): 741–45. http://dx.doi.org/10.4028/www.scientific.net/amr.430-432.741.
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VIP (Vacuum insulation panel), as a high performance insulation component, combine with limited thickness, have recently been introduced to numerous energy conservation applications. VIP consists of a highly insulating core material and a gas tight barrier envelope which is generally composed of plastic film and aluminum film. When the envelope is stainless steel sheet, VIP is called VIS (vacuum insulation sandwich). Because of this hardly permeable rigid barrier, VIS presents more fantastic properties such as resistance against external mechanical loads and penetration of atmospheric gases and water vapor. Consequently, the service life of VIS is significantly longer than that of VIP. Detailed structure and some practical applications of VIS elements are also reviewed in this paper.
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Wong, Xianrong y Colin L. Stewart. "The Laminopathies and the Insights They Provide into the Structural and Functional Organization of the Nucleus". Annual Review of Genomics and Human Genetics 21, n.º 1 (31 de agosto de 2020): 263–88. http://dx.doi.org/10.1146/annurev-genom-121219-083616.
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In recent years, our perspective on the cell nucleus has evolved from the view that it is a passive but permeable storage organelle housing the cell's genetic material to an understanding that it is in fact a highly organized, integrative, and dynamic regulatory hub. In particular, the subcompartment at the nuclear periphery, comprising the nuclear envelope and the underlying lamina, is now known to be a critical nexus in the regulation of chromatin organization, transcriptional output, biochemical and mechanosignaling pathways, and, more recently, cytoskeletal organization. We review the various functional roles of the nuclear periphery and their deregulation in diseases of the nuclear envelope, specifically the laminopathies, which, despite their rarity, provide insights into contemporary health-care issues.
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Olaoye, Toba Samuel, Mark Dewsbury y Hartwig Künzel. "Empirical Investigation of the Hygrothermal Diffusion Properties of Permeable Building Membranes Subjected to Variable Relative Humidity Condition". Energies 14, n.º 13 (5 de julio de 2021): 4053. http://dx.doi.org/10.3390/en14134053.
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Hygrothermal modelling is increasingly used to inform building envelope design. A key input for these calculations is the material’s vapour diffusion properties. Respecting a growing international concern, this research has questioned the appropriateness of the current test method to establish construction material for vapour diffusion properties. This article reports on the empirical measurement of the vapour diffusion properties of two vapour-permeable building membranes commonly used in Australia residential systems when subjected to variable relative humidity conditions. The method involved completing dry cup and wet cup standard tests as specified in ISO 12572, (23 °C and 50% relative humidity RH). Further tests were then conducted as temperature remained at 23 °C but the relative humidity changed to 35%, 65% and 80%, respectively, in order to know if the diffusion properties are the same or change with varying relative humidity. The results from the wet cup and dry cup tests under different relative humidity conditions were non-linear and different. These results indicate vapour-permeable membranes behave differently when exposed to different relative humidity conditions. In conclusion, this research demonstrates that the current vapour resistivity test method is inadequate, hence the need to establish more detailed diffusion resistivity properties in different humidity ranges that represent conditions experienced within a building’s external envelope.
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Lu, Zhi Hong, Hongzhi Xu y Gregory H. Leno. "DNA Replication in Quiescent Cell Nuclei: Regulation by the Nuclear Envelope and Chromatin Structure". Molecular Biology of the Cell 10, n.º 12 (diciembre de 1999): 4091–106. http://dx.doi.org/10.1091/mbc.10.12.4091.
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Quiescent nuclei from differentiated somatic cells can reacquire pluripotence, the capacity to replicate, and reinitiate a program of differentiation after transplantation into amphibian eggs. The replication of quiescent nuclei is recapitulated in extracts derived from activated Xenopus eggs; therefore, we have exploited this cell-free system to explore the mechanisms that regulate initiation of replication in nuclei from terminally differentiatedXenopus erythrocytes. We find that these nuclei lack many, if not all, pre-replication complex (pre-RC) proteins. Pre-RC proteins from the extract form a stable association with the chromatin of permeable nuclei, which replicate in this system, but not with the chromatin of intact nuclei, which do not replicate, even though these proteins cross an intact nuclear envelope. During extract incubation, the linker histones H1 and H10 are removed from erythrocyte chromatin by nucleoplasmin. We show that H1 removal facilitates the replication of permeable nuclei by increasing the frequency of initiation most likely by promoting the assembly of pre-RCs on chromatin. These data indicate that initiation in erythrocyte nuclei requires the acquisition of pre-RC proteins from egg extract and that pre-RC assembly requires the loss of nuclear envelope integrity and is facilitated by the removal of linker histone H1 from chromatin.
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Shankar, V. y C. E. Hagentoft. "Numerical Investigation of Natural Convection in Horizontal Porous Media Heated from Below—Comparisons with Experiments". Journal of Thermal Envelope and Building Science 23, n.º 4 (abril de 2000): 318–38. http://dx.doi.org/10.1177/174425910002300403.
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Thick layers of highly permeable loose-fill insulation are used to thermally insulate attics in modern building technology. Since the use of highly permeable insulation leads to an increase in air movement not only in the porous layer (insulation) but also in the fluid layer (attics), it is therefore of paramount interest to determine the influence of the complex heat transfer phenomena due to natural and forced convection on the thermal properties of insulating porous medium with air cavity. With the help of CFD (Computational Fluid Dynamics), the combined effect of air movement inside the insulation and the air cavity is investigated. The paper deals with the CFD analysis, carried out in order to predict the effects of natural convection on the thermal performance of the building envelope. The results obtained from the numerical computations are compared with experimental findings.
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Koster, Wolfgang,. "Cytoplasmic membrane iron permease systems in the bacterial cell envelope". Frontiers in Bioscience 10, n.º 1-3 (2005): 462. http://dx.doi.org/10.2741/1542.
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Georgatos, S. D., A. Pyrpasopoulou y P. A. Theodoropoulos. "Nuclear envelope breakdown in mammalian cells involves stepwise lamina disassembly and microtubule-drive deformation of the nuclear membrane". Journal of Cell Science 110, n.º 17 (1 de septiembre de 1997): 2129–40. http://dx.doi.org/10.1242/jcs.110.17.2129.
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We have studied nuclear envelope disassembly in mammalian cells by morphological methods. The first signs of nuclear lamina depolymerization become evident in early prophase as A-type lamins start dissociating from the nuclear lamina and diffuse into the nucleoplasm. While B-type lamins are still associated with the inner nuclear membrane, two symmetrical indentations develop on antidiametric sites of the nuclear envelope. These indentations accommodate the sister centrosomes and associated astral microtubules. At mid- to late prophase, elongating microtubules apparently push on the nuclear surface and eventually penetrate the nucleus. At this point the nuclear envelope becomes freely permeable to large ligands, as indicated by experiments with digitonin-treated cells and by the massive release of solubilized A-type lamins into the cytoplasm. At the prophase/prometaphase transition, the B-type lamina is fragmented, but ‘islands’ of lamin B polymer can still be discerned on the tips of congressing chromosomes. Finally, at metaphase, the lamin B polymer breaks down into small pieces, which tend to concentrate in the area of the mitotic spindle. Nuclear envelope breakdown is not prevented when the microtubules are depolymerized by nocodazole; however, the mode of nuclear lamina fragmentation in the absence of microtubules is markedly different from the normal one and involves multiple raffles and gaps, which develop rapidly along the entire surface of the nuclear envelope. These data suggest that nuclear envelope disassembly is a stepwise process in which the microtubules play an important part.
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Harsman, Anke, Annette Schock, Birgit Hemmis, Vanessa Wahl, Ingrid Jeshen, Philipp Bartsch, Armin Schlereth et al. "OEP40, a Regulated Glucose-permeable β-Barrel Solute Channel in the Chloroplast Outer Envelope Membrane". Journal of Biological Chemistry 291, n.º 34 (23 de junio de 2016): 17848–60. http://dx.doi.org/10.1074/jbc.m115.712398.
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Ziegenfuss, Jeanette Y., Jon C. Tilburt, Kandace Lackore, Sarah Jenkins, Katherine James y Timothy J. Beebe. "Envelope Type and Response Rates in a Survey of Health Professionals". Field Methods 26, n.º 4 (8 de abril de 2014): 380–89. http://dx.doi.org/10.1177/1525822x14527726.
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Surveys are an important tool for assessing physician and nursing professionals’ practice patterns and guideline adherence. Obtaining quality survey data consisting of low item and unit nonresponse remains a persistent challenge in these populations. We tested the relative impact of two envelope types (padded vs. priority mail) on unit and item nonresponse in a survey of Minnesota health care workers. Respondents were randomized to receive a survey in one of two envelope types: a padded 8.5′′ × 11′′ envelope or a similarly sized priority mail envelope. After the first mailing, the response rate was 53.9% and did not differ across envelope conditions. Females and RNs were more likely to respond to the priority envelope than the padded envelope, but this finding did not hold in multivariate analysis. There was no difference in item nonresponse across the two envelope conditions. It may be that our two approaches were not enough to permeate the semi-porous membrane of gatekeeping that has been posited as a driver of low physician survey response rates relative to those observed in the general population. Nonetheless, our findings suggest that packaging may matter for some populations and not others.
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Leontiev, A. I. y A. F. Polyakov. "Simulation of internal heat transfer in a porous permeable envelope at low values of Reynolds number". High Temperature 46, n.º 6 (30 de noviembre de 2008): 811–26. http://dx.doi.org/10.1134/s0018151x08060114.
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Alongi, Andrea y Livio Mazzarella. "The Dual Air Vented Thermal Box: A Laboratory Apparatus to Test Air Permeable Building Envelope Technologies". Energy Procedia 78 (noviembre de 2015): 1543–48. http://dx.doi.org/10.1016/j.egypro.2015.11.198.
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Tsuhako, Maria H., Luis Carlos S. Ferreira y Sérgio Olavo P. da Costa. "OppA Escherichia coli mutants have osmodependent resistance to aminoglycoside antibiotics". Genetics and Molecular Biology 21, n.º 1 (marzo de 1998): 15–19. http://dx.doi.org/10.1590/s1415-47571998000100004.
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The oligopeptide permease (OppA) protein was found to be missing in the periplasmic fractions of Escherichia coli kanamycin-resistant mutants selected under high osmotic conditions. The growth behavior of one mutant in media containing kanamycin or the toxic peptide triornithine suggests that OppA and another cell envelope component contribute to the osmolarity-dependent aminoglycoside resistance of E. Coli.
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Paddy, M. R., H. Saumweber, D. A. Agard y J. W. Sedat. "Time-resolved, in vivo studies of mitotic spindle formation and nuclear lamina breakdown in Drosophila early embryos". Journal of Cell Science 109, n.º 3 (1 de marzo de 1996): 591–607. http://dx.doi.org/10.1242/jcs.109.3.591.
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Time-resolved, two-component, three-dimensional fluorescence light microscopy imaging in living Drosophila early embryos is used to demonstrate that a large fraction of the nuclear envelope lamins remain localized to a rim in the nuclear periphery until well into metaphase. The process of lamin delocalization and dispersal, typical of ‘open’ forms of mitosis, does not begin until about the time the final, metaphase geometry of the mitotic spindle is attained. Lamin dispersal is completed about the time that the chromosomal movements of anaphase begin. This pattern of nuclear lamina breakdown appears to be intermediate between traditional designations of ‘open’ and ‘closed’ mitoses. These results thus clarify earlier observations of lamins in mitosis in fixed Drosophila early embryos, clearly showing that the observed lamin localization does not result from a structurally defined ‘spindle envelope’ that persists throughout mitosis. During this extended time interval of lamin localization in the nuclear periphery, the lamina undergoes an extensive series of structural rearrangements that are closely coupled to, and likely driven by, the movements of the centrosomes and microtubules that produce the mitotic spindle. Furthermore, throughout this time the nuclear envelope structure is permeable to large macromolecules, which are excluded in interphase. While the functional significance of these structural dynamics is not yet clear, it is consistent with a functional role for the lamina in mitotic spindle formation.
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Dadras Chomachayi, Masoud, Pierre Blanchet y Atif Hussain. "Development of bio-based membranes for building envelope applications from poly(lactic acid) and cellulose microfibers". BioResources 17, n.º 4 (12 de agosto de 2022): 5707–27. http://dx.doi.org/10.15376/biores.17.4.5707-5727.
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A bio-based membrane was developed for building envelope applications. Biocomposites with enhanced water vapor permeability were fabricated based on poly(lactic acid) (PLA) and cellulose microfibers (CMF). To improve the interfacial adhesion between PLA and fibers, polyethylene glycol (PEG) was used as a compatibilizer for the modification of CMF. The properties of prepared PLA-based biocomposites were investigated in terms of their morphology, thermal stability, thermomechanical properties, and water vapor permeability. The morphological investigation showed the improved dispersion of cellulose fibers in the PLA matrix after modification of the bio-filler with PEG. The thermogravimetric analysis illustrated that the addition of modified CMFs increased the thermal stability of materials. Moreover, the water vapor permeability of PLA-based biocomposites was enhanced by adding modified CMFs to the PLA matrix. The results suggest that the utilization of PEG as a biopolymer compatibilizer represents a cost-effective and environmentally friendly method to improve the properties of PLA/CMF biocomposites. The developed membranes are potential materials for the fabrication of bio-based membranes with permeable properties that facilitate the transmission of entrapped water vapor through the building, eventually prolonging the service life of building envelope materials.
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Simonson, Carey J., Mikael Salonvaara y Tuomo Ojanen. "Heat and Mass Transfer between Indoor Air and a Permeable and Hygroscopic Building Envelope: Part I – Field Measurements". Journal of Thermal Envelope and Building Science 28, n.º 1 (julio de 2004): 63–101. http://dx.doi.org/10.1177/1097196304044395.
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Zhang, Chong, Jinbo Wang, Liao Li y Wenjie Gang. "Dynamic thermal performance and parametric analysis of a heat recovery building envelope based on air-permeable porous materials". Energy 189 (diciembre de 2019): 116361. http://dx.doi.org/10.1016/j.energy.2019.116361.
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Bastien, Diane y Martin Winther-Gaasvig. "Influence of driving rain and vapour diffusion on the hygrothermal performance of a hygroscopic and permeable building envelope". Energy 164 (diciembre de 2018): 288–97. http://dx.doi.org/10.1016/j.energy.2018.07.195.
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Feldherr, C. M. y D. Akin. "The permeability of the nuclear envelope in dividing and nondividing cell cultures." Journal of Cell Biology 111, n.º 1 (1 de julio de 1990): 1–8. http://dx.doi.org/10.1083/jcb.111.1.1.
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The objective of this study was to determine whether the permeability characteristics of the nuclear envelope vary during different phases of cellular activity. Both passive diffusion and signal-mediated transport across the envelope were analyzed during the HeLa cell cycle, and also in dividing, confluent (growth-arrested), and differentiated 3T3-L1 cultures. Colloidal gold stabilized with BSA was used to study diffusion, whereas transport was investigated using gold particles coated with nucleoplasmin, a karyophilic Xenopus oocyte protein. The gold tracers were microinjected into the cytoplasm, and subsequently localized within the cells by electron microscopy. The rates of diffusion in HeLa cells were greatest during the first and fifth hours after the onset of anaphase. These results correlate directly with the known rates of pore formation, suggesting that pores are more permeable during or just after reformation. Signal-mediated transport in HeLa cells occurs through channels that are located within the pore complexes and have functional diameters up to 230-250 A. Unlike diffusion, no significant differences in transport were observed during different phases of the cell cycle. A comparison of dividing and confluent 3T3-L1 cultures revealed highly significant differences in the transport of nucleoplasmin-gold across the envelope. The nuclei of dividing cells not only incorporated larger particles (230 A versus 190 A in diameter, including the protein coat), but the relative uptake of the tracer was about seven times greater than that in growth-arrested cells. Differentiation of confluent cells to adipocytes was accompanied by an increase in the maximum diameter of the transport channel to approximately 230 A.
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Gu, Qian, Yue Wang, Bin Tan y Sheng Ren. "Analysis of Heat Transfer by Thermal Bridge of Corner Wall in a New Glass Regenerated Pumice External Wall System". Applied Mechanics and Materials 291-294 (febrero de 2013): 954–59. http://dx.doi.org/10.4028/www.scientific.net/amm.291-294.954.
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This paper was based on heat insulating members made by a new type of waste glass regenerative pumice, with the characteristics of light weight, permeable water retention, ventilation, heat insulation, fire retardant, etc. In the external wall heat insulating system of building envelops, the thermal bridge of external wall corner was simulated with ANSYS. The temperature field and flux field distribution will be shown respectively of non-insulation, self-insulation, internal insulation and external insulation. Through comparing the heat preservation of different insulation forms, the external insulation was better than internal insulation and self-insulation. Besides, considering the imperfection of calculating the wall average heat transfer coefficient in current energy saving standards, a simplified method was presented to calculate the linear heat transmission coefficient with ANSYS. The two coefficients were compared to serve the latest research.
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MIKHASEK, Andrey A. y Nikolay R. MALYUGIN. "INFLUENCE OF FILTRATION IN THE BODY OF AN ACTIVE PROTECTIVE STRUCTURE ON THE FLOW CHARACTERISTICS". Urban construction and architecture 9, n.º 3 (15 de septiembre de 2019): 92–98. http://dx.doi.org/10.17673/vestnik.2019.03.12.
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The article describes the numerical model of the fl ow that envelops the shore protection structure in the form of a stream spur. Various from the point of view of permeability, spur body material options are considered. To model turbulent fi ltration as local resistance in the fl ow, a formula is proposed that relates the fi ltration coeffi - cient to the hydraulic resistance coeffi cient of a permeable medium. As a result of the simulation, images were obtained in the form of a planned distribution of velocities and pressures in the vicinity of the structure. The obtained materials indicate the relative position of the transit and whirlpool zones of the fl ow. Conclusions are drawn about the nature of the stream fl owing around the shore protection structure and the eff ect of fi ltration in the body of the structure on the characteristics of this stream.
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Simonson, Carey J., Mikael Salaonvaara y Tuomo Ojanen. "Heat and Mass Transfer between Indoor Air and a Permeable and Hygroscopic Building Envelope: Part II – Verification and Numerical Studies". Journal of Thermal Envelope and Building Science 28, n.º 2 (octubre de 2004): 161–85. http://dx.doi.org/10.1177/1097196304044397.
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Lambrechts, S. A. G., M. C. G. Aalders y J. Van Marle. "Mechanistic Study of the Photodynamic Inactivation of Candida albicans by a Cationic Porphyrin". Antimicrobial Agents and Chemotherapy 49, n.º 5 (mayo de 2005): 2026–34. http://dx.doi.org/10.1128/aac.49.5.2026-2034.2005.
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ABSTRACT The growing resistance against antifungal agents has renewed the search for alternative treatment modalities, and antimicrobial photodynamic inactivation (PDI) is a potential candidate. The cationic porphyrin 5-phenyl-10,15,20-Tris(N-methyl-4-pyridyl)porphyrin chloride (TriP[4]) is a photosensitizer that in combination with light can inactivate bacteria, fungi, and viruses. For future improvement of the efficacy of PDI of clinically relevant fungi such as Candida albicans, we sought to understand the working mechanism by following the response of C. albicans exposed to PDI using fluorescence confocal microscopy and freeze-fracture electron microscopy. The following events were observed under dark conditions: TriP[4] binds to the cell envelope of C. albicans, and none or very little TriP[4] enters the cell. Upon illumination the cell membrane is damaged and eventually becomes permeable for TriP[4]. After lethal membrane damage, a massive influx of TriP[4] into the cell occurs. Only the vacuole membrane is resistant to PDI-induced damage once TriP[4] passes the plasma membrane. Increasing the incubation time of C. albicans with TriP[4] prior to illumination did not increase the influx of TriP[4] into the cell or the efficacy of PDI. After the replacement of 100% phosphate-buffered saline (PBS) by 10% PBS as the medium, C. albicans became permeable for TriP[4] during dark incubation and the efficacy of PDI increased dramatically. In conclusion, C. albicans can be successfully inactivated by the cationic porphyrin TriP[4], and the cytoplasmic membrane is the target organelle. TriP[4] influx occurred only after cell death.
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Kivelä, Hanna M., Rimantas Daugelavičius, Riina H. Hankkio, Jaana K. H. Bamford y Dennis H. Bamford. "Penetration of Membrane-Containing Double-Stranded-DNA Bacteriophage PM2 into Pseudoalteromonas Hosts". Journal of Bacteriology 186, n.º 16 (15 de agosto de 2004): 5342–54. http://dx.doi.org/10.1128/jb.186.16.5342-5354.2004.
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ABSTRACT The icosahedral bacteriophage PM2 has a circular double-stranded DNA (dsDNA) genome and an internal lipid membrane. It is the only representative of the Corticoviridae family. How the circular supercoiled genome residing inside the viral membrane is translocated into the gram-negative marine Pseudoalteromonas host has been an intriguing question. Here we demonstrate that after binding of the virus to an abundant cell surface receptor, the protein coat is most probably dissociated. During the infection process, the host cell outer membrane becomes transiently permeable to lipophilic gramicidin D molecules proposing fusion with the viral membrane. One of the components of the internal viral lipid core particle is the integral membrane protein P7, with muralytic activity that apparently aids the process of peptidoglycan penetration. Entry of the virion also causes a limited depolarization of the cytoplasmic membrane. These phenomena differ considerably from those observed in the entry process of bacteriophage PRD1, a dsDNA virus, which uses its internal membrane to make a cell envelope-penetrating tubular structure.
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Shah, Pramod y Chien-Sheng Chen. "Systematic Screening of Penetratin’s Protein Targets by Yeast Proteome Microarrays". International Journal of Molecular Sciences 23, n.º 2 (10 de enero de 2022): 712. http://dx.doi.org/10.3390/ijms23020712.
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Cell-penetrating peptides (CPPs) have distinct properties to translocate across cell envelope. The key property of CPPs to translocation with attached molecules has been utilized as vehicles for the delivery of several potential drug candidates that illustrate the significant effect in in-vitro experiment but fail in in-vivo experiment due to selectively permeable nature of cell envelop. Penetratin, a well-known CPP identified from the third α-helix of Antennapedia homeodomain of Drosophila, has been widely used and studied for the delivery of bioactive molecules to treat cancers, stroke, and infections caused by pathogenic organisms. Few studies have demonstrated that penetratin directly possesses antimicrobial activities against bacterial and fungal pathogens; however, the mechanism is unknown. In this study, we have utilized the power of high-throughput Saccharomyces cerevisiae proteome microarrays to screen all the potential protein targets of penetratin. Saccharomyces cerevisiae proteome microarrays assays of penetratin followed by statistical analysis depicted 123 Saccharomyces cerevisiae proteins as the protein targets of penetratin out of ~5800 Saccharomyces cerevisiae proteins. To understand the target patterns of penetratin, enrichment analyses were conducted using 123 protein targets. In biological process: ribonucleoprotein complex biogenesis, nucleic acid metabolic process, actin filament-based process, transcription, DNA-templated, and negative regulation of gene expression are a few significantly enriched terms. Cytoplasm, nucleus, and cell-organelles are enriched terms for cellular component. Protein-protein interactions network depicted ribonucleoprotein complex biogenesis, cortical cytoskeleton, and histone binding, which represent the major enriched terms for the 123 protein targets of penetratin. We also compared the protein targets of penetratin and intracellular protein targets of antifungal AMPs (Lfcin B, Histatin-5, and Sub-5). The comparison results showed few unique proteins between penetratin and AMPs. Nucleic acid metabolic process and cellular component disassembly were the common enrichment terms for penetratin and three AMPs. Penetratin shows unique enrichment items that are related to DNA biological process. Moreover, motif enrichment analysis depicted different enriched motifs in the protein targets of penetratin, LfcinB, Histatin-5, and Sub-5.
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Tugizov, Sharof, Ekaterina Maidji, Jianqiao Xiao, Zhenwei Zheng y Lenore Pereira. "Human Cytomegalovirus Glycoprotein B Contains Autonomous Determinants for Vectorial Targeting to Apical Membranes of Polarized Epithelial Cells". Journal of Virology 72, n.º 9 (1 de septiembre de 1998): 7374–86. http://dx.doi.org/10.1128/jvi.72.9.7374-7386.1998.
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ABSTRACT We previously reported that human cytomegalovirus (CMV) glycoprotein B (gB) is vectorially transported to apical membranes of CMV-infected polarized human retinal pigment epithelial cells propagated on permeable filter supports and that virions egress predominantly from the apical membrane domain. In the present study, we investigated whether gB itself contains autonomous information for apical transport by expressing the molecule in stably transfected Madine-Darby canine kidney (MDCK) cells grown on permeable filter supports. Laser scanning confocal immunofluorescence microscopy and domain-selective biotinylation of surface membrane domains showed that CMV gB was transported to apical membranes independently of other envelope glycoproteins and that it colocalized with proteins in transport vesicles of the biosynthetic and endocytic pathways. Determinants for trafficking to apical membranes were located by evaluating the targeting of gB derivatives with deletions in the lumen, transmembrane (TM) anchor, and carboxyl terminus. Derivative gB(Δ717-747), with an internal deletion in the luminal juxtamembrane sequence that preserved the N- andO-glycosylation sites, retained vectorial transport to apical membranes. In contrast, derivatives that lacked the TM anchor and cytosolic domain (gBΔ646-906) or the TM anchor alone (gBΔ751-771) underwent considerable basolateral targeting. Likewise, derivatives lacking the entire cytosolic domain (gBΔ772-906) or the last 73 amino acids (gBΔ834-906) showed disrupted apical transport. Site-specific mutations that deleted or altered the cluster of acidic residues with a casein kinase II phosphorylation site at the extreme carboxyl terminus, which can serve as an internalization signal, caused partial missorting of gB to basolateral membranes. Our studies indicate that CMV gB contains autonomous information for apical targeting in luminal, TM anchor, and cytosolic domain sequences, forming distinct structural elements that cooperate in vectorial transport in polarized epithelial cells.
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Lénárt, Péter, Gwénaël Rabut, Nathalie Daigle, Arthur R. Hand, Mark Terasaki y Jan Ellenberg. "Nuclear envelope breakdown in starfish oocytes proceeds by partial NPC disassembly followed by a rapidly spreading fenestration of nuclear membranes". Journal of Cell Biology 160, n.º 7 (24 de marzo de 2003): 1055–68. http://dx.doi.org/10.1083/jcb.200211076.
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Breakdown of the nuclear envelope (NE) was analyzed in live starfish oocytes using a size series of fluorescently labeled dextrans, membrane dyes, and GFP-tagged proteins of the nuclear pore complex (NPC) and the nuclear lamina. Permeabilization of the nucleus occurred in two sequential phases. In phase I the NE became increasingly permeable for molecules up to ∼40 nm in diameter, concurrent with a loss of peripheral nuclear pore components over a time course of 10 min. The NE remained intact on the ultrastructural level during this time. In phase II the NE was completely permeabilized within 35 s. This rapid permeabilization spread as a wave from one epicenter on the animal half across the nuclear surface and allowed free diffusion of particles up to ∼100 nm in diameter into the nucleus. While the lamina and nuclear membranes appeared intact at the light microscopic level, a fenestration of the NE was clearly visible by electron microscopy in phase II. We conclude that NE breakdown in starfish oocytes is triggered by slow sequential disassembly of the NPCs followed by a rapidly spreading fenestration of the NE caused by the removal of nuclear pores from nuclear membranes still attached to the lamina.
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Lu, Binbin, Changcheng Xu, Koichiro Awai, A. Daniel Jones y Christoph Benning. "A Small ATPase Protein of Arabidopsis, TGD3, Involved in Chloroplast Lipid Import". Journal of Biological Chemistry 282, n.º 49 (15 de octubre de 2007): 35945–53. http://dx.doi.org/10.1074/jbc.m704063200.
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Polar lipid trafficking is essential in eukaryotic cells as membranes of lipid assembly are often distinct from final destination membranes. A striking example is the biogenesis of the photosynthetic membranes (thylakoids) in plastids of plants. Lipid biosynthetic enzymes at the endoplasmic reticulum and the inner and outer plastid envelope membranes are involved. This compartmentalization requires extensive lipid trafficking. Mutants of Arabidopsis are available that are disrupted in the incorporation of endoplasmic reticulum-derived lipid precursors into thylakoid lipids. Two proteins affected in two of these mutants, trigalactosyldiacylglycerol 1 (TGD1) and TGD2, encode the permease and substrate binding component, respectively, of a proposed lipid translocator at the inner chloroplast envelope membrane. Here we describe a third protein of Arabidopsis, TGD3, a small ATPase proposed to be part of this translocator. As in the tgd1 and tgd2 mutants, triacylglycerols and trigalactolipids accumulate in a tgd3 mutant carrying a T-DNA insertion just 5′ of the TGD3 coding region. The TGD3 protein shows basal ATPase activity and is localized inside the chloroplast beyond the inner chloroplast envelope membrane. Proteins orthologous to TGD1, -2, and -3 are predicted to be present in Gram-bacteria, and the respective genes are organized in operons suggesting a common biochemical role for the gene products. Based on the current analysis, it is hypothesized that TGD3 is the missing ATPase component of a lipid transporter involving TGD1 and TGD2 required for the biosynthesis of ER-derived thylakoid lipids in Arabidopsis.
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Strandin, Tomas, Jussi Hepojoki, Hao Wang, Antti Vaheri y Hilkka Lankinen. "Inactivation of hantaviruses by N-ethylmaleimide preserves virion integrity". Journal of General Virology 92, n.º 5 (1 de mayo de 2011): 1189–98. http://dx.doi.org/10.1099/vir.0.027896-0.
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Thiol groups of cysteine residues are crucial for the infectivity of various enveloped viruses, but their role in the infectivity of viruses of the family Bunyaviridae has thus far not been studied. This report shows that thiol groups are essential to the infectivity of hantaviruses. Alkylation of the thiol functional groups using the membrane-permeable compound N-ethylmaleimide (NEM) and membrane-impermeable compound 5,5′-dithio-bis-(2-nitrobenzoic acid) (DTNB) showed NEM to be a highly effective inactivator of Puumala and Tula hantaviruses. The NEM-inactivated hantavirus maintained the buoyant density of the wild-type virus. Furthermore, the antigenicity of glycoproteins and the cell attachment capacity of virions were retained at NEM concentrations that totally abolished virus infectivity. These results signified preservation of virion integrity following inactivation with NEM, making chemically inactivated virions valuable research antigens. It was demonstrated with biotin-conjugated maleimide, a mechanistic analogue of NEM, that all the structural proteins of hantavirus were sensitive towards thiol alkylation. In contrast to hantaviruses, NEM did not abolish Uukuniemi phlebovirus infectivity to the same extent. This indicates differences in the use of free thiols in virus entry among members of the family Bunyaviridae.
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Ibe, Ekaterina, Galina Shibaeva, Svyatoslav Mironov y Danil Litvin. "Problems of thermal protection of two-layer external walls with hinged facade systems". E3S Web of Conferences 263 (2021): 02013. http://dx.doi.org/10.1051/e3sconf/202126302013.
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Currently, in the Republic of Khakassia, much attention is paid to research aimed at reducing air pollution due to fuel combustion. In this aspect, the issue of increasing the energy efficiency of buildings is relevant. The use of ventilated facade systems with an air gap makes it possible to improve the energy efficiency class of buildings and modernize the facades. However, these facade systems have weak points that require detailed and high-quality study. Often, design solutions are used that are used in warm climates without taking into account the peculiarities of a cold climate - frequent changes in temperature, humidity, wind loads, and other influences, which can lead to negative manifestations. Facade systems with a ventilated air gap must provide the ability to monitor the operability of all system elements and, if necessary, carry out repair and reconstruction work with minimal operating costs. The article presents an analysis of the thermal properties of an external fence using a hinged facade structure. The influence of installation defects and heat-conducting inclusions on the heat-shielding properties of the building envelope is shown. It was determined that during operation the moisture-windproof membrane loses its vapor-permeable properties.
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Torres-Ramo, Joaquín, Purificación González-Martínez, Nerea Arriazu-Ramos y Ana Sánchez-Ostiz. "Influence of the Water Vapour Permeability of Airtight Sheets on the Behaviour of Facade". Sustainability 12, n.º 24 (15 de diciembre de 2020): 10480. http://dx.doi.org/10.3390/su122410480.
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The air-tightness of the thermal envelope of buildings is one of the measures to reduce their energy demands in order to achieve global warming reduction targets. To this end, airtight sheets with different water vapour permeability characteristics are used. The different products studied are highly dispersed in terms of equivalent air thickness values, leading to confusion. After the analysis carried out, it is concluded that all airtight sheets are vapour barriers. To clarify whether or not these sheets are necessary as vapour barriers, a condensation analysis was carried out on 13 different facades for 3 climate zones with severe winters as defined in Spanish regulations. The results reveal that interstitial condensation occurs in only 7 of the 39 case studies, with the traditional facades of brickwork with render causing the greatest problems if the appropriate products are not used. In these cases, airtight sheets with water vapour barrier characteristics must be applied on the interior face of the insulating material. In all other cases (32), the airtight sheets must be permeable to water vapour if it is looked for a more breathable wall to water vapour and a better control of the interior humidity conditions.
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Gems, Bernhard, Bruno Mazzorana, Thomas Hofer, Michael Sturm, Roman Gabl y Markus Aufleger. "3-D hydrodynamic modelling of flood impacts on a building and indoor flooding processes". Natural Hazards and Earth System Sciences 16, n.º 6 (14 de junio de 2016): 1351–68. http://dx.doi.org/10.5194/nhess-16-1351-2016.
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Abstract. Given the current challenges in flood risk management and vulnerability assessment of buildings exposed to flood hazards, this study presents three-dimensional numerical modelling of torrential floods and its interaction with buildings. By means of a case study application, the FLOW-3D software is applied to the lower reach of the Rio Vallarsa torrent in the village of Laives (Italy). A single-family house on the flood plain is therefore considered in detail. It is exposed to a 300-year flood hydrograph. Different building representation scenarios, including an entire impervious building envelope and the assumption of fully permeable doors, light shafts and windows, are analysed. The modelling results give insight into the flooding process of the building's interior, the impacting hydrodynamic forces on the exterior and interior walls, and further, they quantify the impact of the flooding of a building on the flow field on the surrounding flood plain. The presented study contributes to the development of a comprehensive physics-based vulnerability assessment framework. For pure water floods, this study presents the possibilities and limits of advanced numerical modelling techniques within flood risk management and, thereby, the planning of local structural protection measures.
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Olaoye, Toba Samuel, Mark Dewsbury, Louise Wallis y Hartwig Küenzel. "Hygrothermal Modelling of the Differences between Single versus Variable Relative Humidity Vapour Diffusion Resistivity Properties of Pliable Membranes". CivilEng 3, n.º 3 (10 de agosto de 2022): 687–716. http://dx.doi.org/10.3390/civileng3030040.
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The study investigates through hygrothermal modelling the effect of different boundary conditions and varying measured vapour diffusion resistivity values on the hygrothermal performance of five pliable membranes. Previously, this research quantified the variable water vapour diffusion resistivity properties of five different pliable building membranes. The membranes were assessed under varying humidity conditions using the gravimetric wet and dry cup test method. The varying humidity conditions better represent the boundary conditions experienced by materials in the building envelope. The pliable membranes include two permeable, two impermeable, and one variable products, which are commonly used to provide air and vapour control layers in the construction of framed external wall systems. This article focusses on the transient hygrothermal modelling of each of these membranes as a component of a typical timber-framed, clay brick veneer external wall system. The simulations were completed for three different climate types, namely, hot and humid, temperate, and cool-temperate with snow, and with a northern and western orientation. The results from hygrothermal and bio-hygrothermal simulations highlighted different responses subject to climate type and orientation. These results show that there are significant differences in simulated moisture and mould growth risk between the results of pliable membranes with single vapour resistance factor value and pliable membranes with multipoint vapour resistance factor values.
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Strambio-de-Castillia, Caterina, Günter Blobel y Michael P. Rout. "Proteins Connecting the Nuclear Pore Complex with the Nuclear Interior". Journal of Cell Biology 144, n.º 5 (8 de marzo de 1999): 839–55. http://dx.doi.org/10.1083/jcb.144.5.839.
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While much has been learned in recent years about the movement of soluble transport factors across the nuclear pore complex (NPC), comparatively little is known about intranuclear trafficking. We isolated the previously identified Saccharomyces protein Mlp1p (myosin-like protein) by an assay designed to find nuclear envelope (NE) associated proteins that are not nucleoporins. We localized both Mlp1p and a closely related protein that we termed Mlp2p to filamentous structures stretching from the nucleoplasmic face of the NE into the nucleoplasm, similar to the homologous vertebrate and Drosophila Tpr proteins. Mlp1p can be imported into the nucleus by virtue of a nuclear localization sequence (NLS) within its COOH-terminal domain. Overexpression experiments indicate that Mlp1p can form large structures within the nucleus which exclude chromatin but appear highly permeable to proteins. Remarkably, cells harboring a double deletion of MLP1 and MLP2 were viable, although they showed a slower net rate of active nuclear import and faster passive efflux of a reporter protein. Our data indicate that the Tpr homologues are not merely NPC-associated proteins but that they can be part of NPC-independent, peripheral intranuclear structures. In addition, we suggest that the Tpr filaments could provide chromatin-free conduits or tracks to guide the efficient translocation of macromolecules between the nucleoplasm and the NPC.
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Kendirgi, Frederic, Dianne M. Barry, Eric R. Griffis, Maureen A. Powers y Susan R. Wente. "An essential role for hGle1 nucleocytoplasmic shuttling in mRNA export". Journal of Cell Biology 160, n.º 7 (31 de marzo de 2003): 1029–40. http://dx.doi.org/10.1083/jcb.200211081.
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Gle1 is required for mRNA export in yeast and human cells. Here, we report that two human Gle1 (hGle1) isoforms are expressed in HeLa cells (hGle1A and B). The two encoded proteins are identical except for their COOH-terminal regions. hGle1A ends with a unique four–amino acid segment, whereas hGle1B has a COOH-terminal 43–amino acid span. Only hGle1B, the more abundant isoform, localizes to the nuclear envelope (NE) and pore complex. To test whether hGle1 is a dynamic shuttling transport factor, we microinjected HeLa cells with recombinant hGle1 and conducted photobleaching studies of live HeLa cells expressing EGFP–hGle1. Both strategies show that hGle1 shuttles between the nucleus and cytoplasm. An internal 39–amino acid domain is necessary and sufficient for mediating nucleocytoplasmic transport. Using a cell-permeable peptide strategy, we document a role for hGle1 shuttling in mRNA export. An hGle1 shuttling domain (SD) peptide impairs the export of both total poly(A)+ RNA and the specific dihydrofolate reductase mRNA. Coincidentally, SD peptide–treated cells show decreased endogenous hGle1 localization at the NE and reduced nucleocytoplasmic shuttling of microinjected, recombinant hGle1. These findings pinpoint the first functional motif in hGle1 and link hGle1 to the dynamic mRNA export mechanism.
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Tucker, Allison N., Travis J. Carlson y Aurijit Sarkar. "Challenges in Drug Discovery for Intracellular Bacteria". Pathogens 10, n.º 9 (11 de septiembre de 2021): 1172. http://dx.doi.org/10.3390/pathogens10091172.
Texto completoResumen
Novel drugs are needed to treat a variety of persistent diseases caused by intracellular bacterial pathogens. Virulence pathways enable many functions required for the survival of these pathogens, including invasion, nutrient acquisition, and immune evasion. Inhibition of virulence pathways is an established route for drug discovery; however, many challenges remain. Here, we propose the biggest problems that must be solved to advance the field meaningfully. While it is established that we do not yet understand the nature of chemicals capable of permeating into the bacterial cell, this problem is compounded when targeting intracellular bacteria because we are limited to only those chemicals that can permeate through both human and bacterial outer envelopes. Unfortunately, many chemicals that permeate through the outer layers of mammalian cells fail to penetrate the bacterial cytoplasm. Another challenge is the lack of publicly available information on virulence factors. It is virtually impossible to know which virulence factors are clinically relevant and have broad cross-species and cross-strain distribution. In other words, we have yet to identify the best drug targets. Yes, standard genomics databases have much of the information necessary for short-term studies, but the connections with patient outcomes are yet to be established. Without comprehensive data on matters such as these, it is difficult to devise broad-spectrum, effective anti-virulence agents. Furthermore, anti-virulence drug discovery is hindered by the current state of technologies available for experimental investigation. Antimicrobial drug discovery was greatly advanced by the establishment and standardization of broth microdilution assays to measure the effectiveness of antimicrobials. However, the currently available models used for anti-virulence drug discovery are too broad, as they must address varied phenotypes, and too expensive to be generally adopted by many research groups. Therefore, we believe drug discovery against intracellular bacterial pathogens can be advanced significantly by overcoming the above hurdles.