ABSTRACT
Delivery of drugs to the brain is impeded by the activity of efflux pumps expressed by endothelial cells of brain vasculature. The ATP binding cassette (ABC) transporters, among which ...ABCB1/MDR1 P‐glycoprotein and ABCC1/multidrug resistance‐associated protein 1 are expressed in brain endothelial cells, participate in drug efflux properties of the blood‐brain barrier (BBB). Searches of the EST (expressed sequence tags) database with the conserved ABC domain, conducted to identify other ABC transporters expressed in the BBB, recovered 15 ABC transporter sequences expressed in human brain cDNA libraries. One of these sequences, identical to ABCG2, was highly expressed in cultured human cerebromicrovascular endothelial cells and human brain tissue at both mRNA and protein levels. Overexpression of human ABCG2 in immortalized rat brain endothelial cells resulted in enhanced polarized abluminal to luminal transport of various substrates tested in the in vitro BBB model. Brain vessels extracted from tissue sections of nonmalignant human brain and glioblastoma tomors by laser capture microdissection microscopy and analyzed by real‐time polymerase chain reaction showed higher expression of ABCG2 relative to ABCB1/MDR1 and ABCC1/MRP1. ABCG2 was up‐regulated in both glioblastoma vessels and parenchymal tissue. These studies suggest a role for brain endothelial ABCG2 transporter in modulating drug delivery to the brain and in conferring drug resistance to glioblastomas.
Summary
Testing of stiff physical substructures (PSs) still poses major technical issues that prevent from adopting hybrid simulation (HS) as a standard structural testing method. Firstly, elastic ...deformation of reaction frames, as well as the limited resolution of displacement transducers, deteriorate displacement control accuracy. Secondly, as a consequence of control errors, small perturbations of actuator displacements entail large restoring force oscillations that spuriously excite the higher eigenmodes of the hybrid model. For this reason, in the current practice, force‐controlled hydraulic jacks handle vertical degrees of freedom, which are typically associated with stiff axially loaded members and excluded from the time integration loop. Vertical forces are either kept constant or adjusted during the experiment based on simplified redistribution rules. Besides deterioration of displacement control accuracy, stiff PSs naturally increase the frequency bandwidth of the hybrid model, whose higher eigenfrequencies (divided by the testing time scale) may fall outside the frequency bandwidth of the actuation system, thus destabilizing the HS. This is a collateral issue to which, in the authors' knowledge, no sufficient attention as been dedicated yet, and this paper tries to address it. From this standpoint, we propose component‐mode synthesis as a rigorous approach for deriving reduced‐order physical and numerical substructure mass and stiffness matrices that minimize the frequency bandwidth of the hybrid model. The proposed methodology allowed for performing HSs of a load‐bearing unreinforced masonry structure including both horizontal and vertical degrees of freedom with a standard three‐actuator setup used for cyclic testing.
•Full-scale cyclic shear tests on 10 unreinforced masonry (URM) walls are presented.•Test results are discussed in respect to the most important parameters.•Limited deformation capacity can be ...expected in URM clay block walls.•Current codes of practice overestimate the deformation capacity of URM walls.•Simple model for the estimation of the deformation capacity is presented.
A research project on the displacement capacity of contemporary unreinforced masonry (URM) walls is underway at the Institute of Structural Engineering of ETH Zurich. The development of the basis for the displacement-based design of URM structures is the prime objective of the present project. In the experimental phase of the project, a total of 10 static-cyclic shear tests on full-scale URM walls made of clay and calcium-silicate blocks were performed to investigate the effects of various factors, i.e. unit type, vertical pre-compression level, aspect ratio, size, and boundary conditions, on the displacement capacity of URM walls. This paper presents and discusses the obtained test results. All the walls (regardless of their failure mode) exhibited limited displacement capacity. The test results show that as the vertical pre-compression level increases, the displacement capacity decreases. Furthermore, they indicate a possible reduction in the displacement capacity of URM walls in the case of an increase in the height or a decrease in the aspect ratio, i.e. the height divided by the length. It is also shown that the values recommended by the current codes of practice for the displacement capacity of URM walls cannot be considered as reliable. Finally, a simple empirical model for the displacement capacity of contemporary URM walls is proposed, based on the results obtained from the tests.
CD1 molecules are glycoproteins that present lipid antigens at the cell surface for immunological recognition by specialized populations of T lymphocytes. Prior experimental data suggest a wide ...variety of lipid species can bind to CD1 molecules, but little is known about the characteristics of cellular ligands that are selected for presentation. Here we have molecularly characterized lipids bound to the human CD1d isoform. Ligands were eluted from secreted CD1d molecules and separated by normal phase HPLC, then characterized by mass spectroscopy. A total of 177 lipid species were molecularly identified, comprising glycerophospholipids and sphingolipids. The glycerophospholipids included common diacylglycerol species, reduced forms known as plasmalogens, lyso-phospholipids (monoacyl species), and cardiolipins (tetraacyl species). The sphingolipids included sphingomyelins and glycosylated forms, such as the ganglioside GM3. These results demonstrate that human CD1d molecules bind a surprising diversity of lipid structures within the secretory pathway, including compounds that have been reported to play roles in cancer, autoimmune diseases, lipid signaling, and cell death.
It has long been known that T cells have the potential to modulate hematopoietic response in different ways. More recently, the importance of interleukin (IL)-17-secreting Th17 cells in ...T-cell-mediated regulation of hematopoiesis was indicated by the line of evidence that IL-17 links T-cell function and hematopoiesis through stimulation of granulopoiesis and neutrophil trafficking. Furthermore, our data demonstrated that IL-17 also affects other cells of hematopoietic system, such as erythroid progenitors, as well as mesenchymal stem cells. In order to better understand the regulatory role of IL-17 in hematopoiesis, molecular mechanisms underlying the effects of IL-17 on hematopoietic and mesenchymal stem cells were also studied.
Baniya merchants of the Mughal Empire, burgher merchants of the Swedish Empire, and chonin merchants of the Tokugawa Shogunate had the same questions on their mind as business people do today. To ...which townspeople should I sell my wares? Of folks that buy from me, are there any that might stop buying from me? Which groups buy which goods? Which saris should I show Ranna Devi to make as much money as I can? How much timber will people want in the coming weeks and months? The world has changed over the centuries with globalization, rapid transportation, instantaneous communication, expansive enterprises, and an explosion of data and signals along with ample computation to process them. In this new age, many continue to answer the aforementioned and other critical business questions in the old-fashioned way, i.e., based on intuition, gut instinct, and personal experience. In our globalized world, however, this is not sufficient anymore and it is essential to replace the business person's gut instinct with science. That science is business analytics. Business analytics is a broad umbrella entailing many problems and solutions, such as demand forecasting and conditioning, resource capacity planning, workforce planning, salesforce modeling and optimization, revenue forecasting, customer/product analytics, and enterprise recommender systems. In our department, we are in creasingly directing our focus on developing models and techniques to address such business problems. The goal of this article is to provide the reader with an overview of this interesting new area of research and then hone in on applications that might require the use of sophisticated signal processing methodologies and utilize financial signals as input.
Neuroinflammation has been implicated in various brain pathologies characterized by hypoxia and ischemia. Astroglia play an important role in the initiation and propagation of ...hypoxia/ischemia-induced inflammation by secreting inflammatory chemokines that attract neutrophils and monocytes into the brain. However, triggers of chemokine up-regulation by hypoxia/ischemia in these cells are poorly understood. Hypoxia-inducible factor-1 (HIF-1) is a dimeric transcriptional factor consisting of HIF-1alpha and HIF-1beta subunits. HIF-1 binds to HIF-1-binding sites in the target genes and activates their transcription. We have recently shown that hypoxia-induced expression of IL-1beta in astrocytes is mediated by HIF-1alpha. In this study, we demonstrate the role of HIF-1alpha in hypoxia-induced up-regulation of inflammatory chemokines, human monocyte chemoattractant protein-1 (MCP-1/CCL2) and mouse MCP-5 (Ccl12), in human and mouse astrocytes, respectively.
Primary fetal human astrocytes or mouse astrocytes generated from HIF-1alpha+/+ and HIF-1alpha+/- mice were subjected to hypoxia (<2% oxygen) or 125 muM CoCl2 for 4 h and 6 h, respectively. The expression of HIF-1alpha, MCP-1 and MCP-5 was determined by semi-quantitative RT-PCR, western blot or ELISA. The interaction of HIF-1alpha with a HIF-1-binding DNA sequence was examined by EMSA and supershift assay. HIF-1-binding sequence in the promoter of MCP-1 gene was cloned and transcriptional activation of MCP-1 by HIF-1alpha was analyzed by reporter gene assay.
Sequence analyses identified HIF-1-binding sites in the promoters of MCP-1 and MCP-5 genes. Both hypoxia and HIF-1alpha inducer, CoCl2, strongly up-regulated HIF-1alpha expression in astrocytes. Mouse HIF-1alpha+/- astrocytes had lower basal levels of HIF-1alpha and MCP-5 expression. The up-regulation of MCP-5 by hypoxia or CoCl2 in HIF-1alpha+/+ and HIF-1alpha+/- astrocytes was correlated with the levels of HIF-1alpha in cells. Both hypoxia and CoCl2 also up-regulated HIF-1alpha and MCP-1 expression in human astrocytes. EMSA assay demonstrated that HIF-1 activated by either hypoxia or CoCl2 binds to wild-type HIF-1-binding DNA sequence, but not the mutant sequence. Furthermore, reporter gene assay demonstrated that hypoxia markedly activated MCP-1 transcription but not the mutated MCP-1 promoter in transfected astrocytes.
These findings suggest that both MCP-1 and MCP-5 are HIF-1 target genes and that HIF-1alpha is involved in transcriptional induction of these two chemokines in astrocytes by hypoxia.
Misfolded protein toxicity and failure of protein quality control underlie neurodegenerative diseases including amyotrophic lateral sclerosis and frontotemporal dementia. Here, we identified ...Lethal(3)malignant brain tumor-like protein 1 (L3MBTL1) as a key regulator of protein quality control, the loss of which protected against the proteotoxicity of mutant Cu/Zn superoxide dismutase or C9orf72 dipeptide repeat proteins. L3MBTL1 acts by regulating p53-dependent quality control systems that degrade misfolded proteins. SET domain-containing protein 8, an L3MBTL1-associated p53-binding protein, also regulated clearance of misfolded proteins and was increased by proteotoxicity-associated stresses in mammalian cells. Both L3MBTL1 and SET domain-containing protein 8 were upregulated in the central nervous systems of mouse models of amyotrophic lateral sclerosis and human patients with amyotrophic lateral sclerosis/frontotemporal dementia. The role of L3MBTL1 in protein quality control is conserved from Caenorhabditis elegans to mammalian neurons. These results reveal a protein quality-control pathway that operates in both normal stress response and proteotoxicity-associated neurodegenerative diseases.
Mutant genes that underlie Mendelian forms of amyotrophic lateral sclerosis (ALS) and biochemical investigations of genetic disease models point to potential driver pathophysiological events ...involving endoplasmic reticulum (ER) stress and autophagy. Several steps in these cell biological processes are known to be controlled physiologically by small ADP-ribosylation factor (ARF) signaling. Here, we investigated the role of ARF guanine nucleotide exchange factors (GEFs), cytohesins, in models of ALS. Genetic or pharmacological inhibition of cytohesins protects motor neurons in vitro from proteotoxic insults and rescues locomotor defects in a Caenorhabditis elegans model of disease. Cytohesins form a complex with mutant superoxide dismutase 1 (SOD1), a known cause of familial ALS, but this is not associated with a change in GEF activity or ARF activation. ER stress evoked by mutant SOD1 expression is alleviated by antagonism of cytohesin activity. In the setting of mutant SOD1 toxicity, inhibition of cytohesin activity enhances autophagic flux and reduces the burden of misfolded SOD1. These observations suggest that targeting cytohesins may have potential benefits for the treatment of ALS.
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