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Search Results: 1 - 10 of 4123 matches for " Albert Zlotnik "
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The chemokine and chemokine receptor superfamilies and their molecular evolution
Albert Zlotnik, Osamu Yoshie, Hisayuki Nomiyama
Genome Biology , 2006, DOI: 10.1186/gb-2006-7-12-243
Abstract: The chemokine superfamily includes a large number of ligands that bind to a smaller number of receptors [1,2]. The best known function of the chemokines is the regulation of migration of various cells in the body, hence their name (from 'chemotactic cytokines'). The importance of the chemokines has grown in recent years, as it has become recognized that they are key players in many disease processes, including inflammation, autoimmune disease, infectious diseases (such as HIV/AIDS), and more recently, cancer (in particular in regulating metastasis) [3]. Multiple chemokine ligands can bind to the same receptor; the perceived complexity and promiscuity of receptor binding has often made this field a challenge to understand and given the impression that chemokines lack specific effects. We have now, however, probably identified most human chemokine ligands. The chemokines are small peptides, whereas their receptors are class A G-protein-coupled receptors. They are best known from mammals, but chemokine genes have also been found in chicken, zebrafish, shark and jawless fish genomes, and possible homologs of chemokine receptors have been reported in nematodes. Careful analysis of the members of the superfamily and their receptors shows a logical order to its genomic organization and function, which in turn is the result of evolutionary pressures. Here, we provide a global view of the chemokine and chemokine receptor superfamilies, focusing particularly on the relationship between their evolution and their functions.As shown in Table 1, there are at least 46 chemokine ligands in humans. There are also 18 functionally signaling chemokine receptors (plus one, CXCR7, which has been recently reported as a potential chemokine receptor) and two 'decoy' or 'scavenger' receptors, DARC and D6, which are known to bind several chemokines but do not signal; their function may be to modulate inflammatory responses through their ability to remove chemokine ligands from inflammatory si
Some remarks on discrete and semi-discrete transparent boundary conditions for solving the time-dependent Schr?dinger equation on the half-axis
Alexander Zlotnik,Ilya Zlotnik
Mathematics , 2014,
Abstract: We consider the generalized time-dependent Schr\"odinger equation on the half-axis and a broad family of finite-difference schemes with the discrete transparent boundary conditions (TBCs) to solve it. We first rewrite the discrete TBCs in a simplified form explicit in space step $h$. Next, for a selected scheme of the family, we discover that the discrete convolution in time in the discrete TBC does not depend on $h$ and, moreover, it coincides with the corresponding convolution in the semi-discrete TBC rewritten similarly. This allows us to prove the bound for the difference between the kernels of the discrete convolutions in the discrete and semi-discrete TBCs (for the first time). Numerical experiments on replacing the discrete TBC convolutions by the semi-discrete one exhibit truly small absolute errors though not relative ones in general. The suitable discretization in space of the semi-discrete TBC for the higher-order Numerov scheme is also discussed.
On the Richardson Extrapolation in Time of Finite Element Method with Discrete TBCs for the Cauchy Problem for the 1D Schr?dinger Equation
A. Zlotnik,I. Zlotnik
Mathematics , 2014,
Abstract: We consider the Cauchy problem for the 1D generalized Schr\"odinger equation on the whole axis. To solve it, any order finite element in space and the Crank-Nicolson in time method with the discrete transparent boundary conditions (TBCs) has recently been constructed. Now we engage the Richardson extrapolation to improve significantly the accuracy in time step. To study its properties, we give results of numerical experiments and enlarged practical error analysis for three typical examples. The resulting method is able to provide high precision results in the uniform norm for reasonable computational costs that is unreachable by more common 2nd order methods in either space or time step. Comparing our results to the previous ones, we obtain much more accurate results using much less amount of both elements and time steps.
On the rate of the volume growth for symmetric viscous heat-conducting gas flows with a free boundary
Alexander Zlotnik
Abstract and Applied Analysis , 2006, DOI: 10.1155/aaa/2006/16071
Abstract: The system of quasilinear equations for symmetric flows of aviscous heat-conducting gas with a free external boundary isconsidered. For global in time weak solutions having nonstrictlypositive density, the linear in time two-sided bounds for the gasvolume growth are established.
On the rate of the volume growth for symmetric viscous heat-conducting gas flows with a free boundary
Alexander Zlotnik
Abstract and Applied Analysis , 2006,
Abstract: The system of quasilinear equations for symmetric flows of a viscous heat-conducting gas with a free external boundary is considered. For global in time weak solutions having nonstrictly positive density, the linear in time two-sided bounds for the gas volume growth are established.
On Error Estimates of the Crank-Nicolson-Polylinear Finite Element Method with the Discrete TBC for the Generalized Schr?dinger Equation in an Unbounded Parallelepiped
Alexander Zlotnik
Mathematics , 2015,
Abstract: We deal with an initial-boundary value problem for the generalized time-dependent Schr\"odinger equation with variable coefficients in an unbounded $n$--dimensional parallelepiped ($n\geq 1$). To solve it, the Crank-Nicolson in time and the polylinear finite element in space method with the discrete transpa\-rent boundary conditions is considered. We present its stability properties and derive new error estimates $O(\tau^2+|h|^2)$ uniformly in time in $L^2$ space norm, for $n\geq 1$, and mesh $H^1$ space norm, for $1\leq n\leq 3$ (a superconvergence result), under the Sobolev-type assumptions on the initial function. Such estimates are proved for methods with the discrete TBCs for the first time.
Voltage-gated sodium channels in taste bud cells
Na Gao, Min Lu, Fernando Echeverri, Bianca Laita, Dalia Kalabat, Mark E Williams, Peter Hevezi, Albert Zlotnik, Bryan D Moyer
BMC Neuroscience , 2009, DOI: 10.1186/1471-2202-10-20
Abstract: We describe the molecular and histological expression profiles of cation channels involved in electrical signal transmission from apical to basolateral membrane domains. TRPM5 was positioned immediately beneath tight junctions to receive calcium signals originating from sweet, bitter, and umami receptor activation, while PKD2L1 was positioned at the taste pore. Using mouse taste bud and lingual epithelial cells collected by laser capture microdissection, SCN2A, SCN3A, and SCN9A voltage-gated sodium channel transcripts were expressed in taste tissue. SCN2A, SCN3A, and SCN9A were expressed beneath tight junctions in subsets of taste cells. SCN3A and SCN9A were expressed in TRPM5 cells, while SCN2A was expressed in TRPM5 and PKD2L1 cells. HCN4, a gene previously implicated in sour taste, was expressed in PKD2L1 cells and localized to cell processes beneath the taste pore.SCN2A, SCN3A and SCN9A voltage-gated sodium channels are positioned to sense initial depolarizing signals stemming from taste receptor activation and initiate taste cell action potentials. SCN2A, SCN3A and SCN9A gene products likely account for the tetrodotoxin-sensitive sodium currents in taste receptor cells.Taste buds house specialized neuroepithelial cells that sense and transmit information regarding the composition of food [1]. These taste cells express receptors for sweet, bitter, umami (the savory taste of glutamate), sour and salty tastants in apical microvilli facing the saliva [2,3]. Following taste receptor activation, taste cells depolarize and fire action potentials resulting in the release of neurotransmitters to nerve fibers innervating basolateral membranes [4,5]. Segregation of taste receptors at the taste pore from the machinery involved in transmitting signals to nerve fibers is mediated by tight junctions, specialized protein networks that separate apical and basolateral membrane domains [6].Information regarding the composition of food flows from the apical to the basolateral doma
Expression of Genes Encoding Multi-Transmembrane Proteins in Specific Primate Taste Cell Populations
Bryan D. Moyer,Peter Hevezi,Na Gao,Min Lu,Dalia Kalabat,Hortensia Soto,Fernando Echeverri,Bianca Laita,Shaoyang Anthony Yeh,Mark Zoller,Albert Zlotnik
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0007682
Abstract: Using fungiform (FG) and circumvallate (CV) taste buds isolated by laser capture microdissection and analyzed using gene arrays, we previously constructed a comprehensive database of gene expression in primates, which revealed over 2,300 taste bud-associated genes. Bioinformatics analyses identified hundreds of genes predicted to encode multi-transmembrane domain proteins with no previous association with taste function. A first step in elucidating the roles these gene products play in gustation is to identify the specific taste cell types in which they are expressed.
Genome-Wide Analysis of Gene Expression in Primate Taste Buds Reveals Links to Diverse Processes
Peter Hevezi, Bryan D. Moyer, Min Lu, Na Gao, Evan White, Fernando Echeverri, Dalia Kalabat, Hortensia Soto, Bianca Laita, Cherry Li, Shaoyang Anthony Yeh, Mark Zoller, Albert Zlotnik
PLOS ONE , 2009, DOI: 10.1371/journal.pone.0006395
Abstract: Efforts to unravel the mechanisms underlying taste sensation (gustation) have largely focused on rodents. Here we present the first comprehensive characterization of gene expression in primate taste buds. Our findings reveal unique new insights into the biology of taste buds. We generated a taste bud gene expression database using laser capture microdissection (LCM) procured fungiform (FG) and circumvallate (CV) taste buds from primates. We also used LCM to collect the top and bottom portions of CV taste buds. Affymetrix genome wide arrays were used to analyze gene expression in all samples. Known taste receptors are preferentially expressed in the top portion of taste buds. Genes associated with the cell cycle and stem cells are preferentially expressed in the bottom portion of taste buds, suggesting that precursor cells are located there. Several chemokines including CXCL14 and CXCL8 are among the highest expressed genes in taste buds, indicating that immune system related processes are active in taste buds. Several genes expressed specifically in endocrine glands including growth hormone releasing hormone and its receptor are also strongly expressed in taste buds, suggesting a link between metabolism and taste. Cell type-specific expression of transcription factors and signaling molecules involved in cell fate, including KIT, reveals the taste bud as an active site of cell regeneration, differentiation, and development. IKBKAP, a gene mutated in familial dysautonomia, a disease that results in loss of taste buds, is expressed in taste cells that communicate with afferent nerve fibers via synaptic transmission. This database highlights the power of LCM coupled with transcriptional profiling to dissect the molecular composition of normal tissues, represents the most comprehensive molecular analysis of primate taste buds to date, and provides a foundation for further studies in diverse aspects of taste biology.
Systematic Identification and Characterization of Novel Human Skin-Associated Genes Encoding Membrane and Secreted Proteins
Peter Arne Gerber, Peter Hevezi, Bettina Alexandra Buhren, Cynthia Martinez, Holger Schrumpf, Marcia Gasis, Susanne Grether-Beck, Jean Krutmann, Bernhard Homey, Albert Zlotnik
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0063949
Abstract: Through bioinformatics analyses of a human gene expression database representing 105 different tissues and cell types, we identified 687 skin-associated genes that are selectively and highly expressed in human skin. Over 50 of these represent uncharacterized genes not previously associated with skin and include a subset that encode novel secreted and plasma membrane proteins. The high levels of skin-associated expression for eight of these novel therapeutic target genes were confirmed by semi-quantitative real time PCR, western blot and immunohistochemical analyses of normal skin and skin-derived cell lines. Four of these are expressed specifically by epidermal keratinocytes; two that encode G-protein-coupled receptors (GPR87 and GPR115), and two that encode secreted proteins (WFDC5 and SERPINB7). Further analyses using cytokine-activated and terminally differentiated human primary keratinocytes or a panel of common inflammatory, autoimmune or malignant skin diseases revealed distinct patterns of regulation as well as disease associations that point to important roles in cutaneous homeostasis and disease. Some of these novel uncharacterized skin genes may represent potential biomarkers or drug targets for the development of future diagnostics or therapeutics.
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