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Single Cells (single + cell)
Terms modified by Single Cells Selected AbstractsPHYLOGENY OF FOUR DINOPHYSIACEAN GENERA (DINOPHYCEAE, DINOPHYSIALES) BASED ON rDNA SEQUENCES FROM SINGLE CELLS AND ENVIRONMENTAL SAMPLES,JOURNAL OF PHYCOLOGY, Issue 5 2009Sara M. Handy Dinoflagellates are a highly diverse and environmentally important group of protists with relatively poor resolution of phylogenetic relationships, particularly among heterotrophic species. We examined the phylogeny of several dinophysiacean dinoflagellates using samples collected from four Atlantic sites. As a rule, 3.5 kb of sequence including the nuclear ribosomal genes SSU, 5.8S, LSU, plus their internal transcribed spacer (ITS) 1 and 2 regions were determined for 26 individuals, including representatives of two genera for which molecular data were previously unavailable, Ornithocercus F. Stein and Histioneis F. Stein. In addition, a clone library targeting the dinophysiacean ITS2 and LSU sequences was constructed from bulk environmental DNA from three sites. Three phylogenetic trees were inferred from the data, one using data from this study for cells identified to genus or species (3.5 kb, 28 taxa); another containing dinoflagellate SSU submissions from GenBank and the 12 new dinophysiacean sequences (1.9 kb, 56 taxa) from this study; and the third tree combing data from identified taxa, dinophysiacean GenBank submissions, and the clone libraries from this study (2.1 kb, 136 taxa). All trees were congruent and indicated a distinct division between the genera Phalacroma F. Stein and Dinophysis Ehrenb. The cyanobionts containing genera Histioneis and Ornithocercus were also monophyletic. This was the largest molecular phylogeny of dinophysoid taxa performed to date and was consistent with the view that the genus Phalacroma may not be synonymous with Dinophysis. [source] Manipulation of Intracellular Auxin in a Single Cell by Light with Esterase-Resistant Caged AuxinsCHEMBIOCHEM, Issue 13 2009Naoyuki Kusaka Abstract Auxin, a plant hormone, is polar transported from its site of production. This auxin polar transport system establishes an auxin gradient in plant tissue that is necessary for proper plant development. Therefore, the spatial effect of the auxin gradient on plant development is highly important for the understanding of plant auxin responses. Herein we report the design, syntheses and biological properties of esterase-resistant caged auxins. The conventional caging group, 2-nitrobenzyl ester, was found to be enzymatically hydrolyzed in plant cells and released original auxin without photolysis. The esterase-resistant caging group, (2,5-dimethoxyphenyl)(2-nitrobenzyl) ester, (DMPNB) was designed to improve the stability of caged auxins. Three auxins, indole 3-acetic acid, naphthalene 1-acetic acid and 2,4-dichlorophenoxy acetic acid were caged with the DMPNB caging group. DMPNB-caged auxins were inactive within a plant cell until photolysis, but they release auxins with photoirradiation to activate auxin-responsive gene expression. We demonstrated spatial and temporal control of intracellular auxin levels with photoirradiation by using this caged auxin system and were able to photocontrol the physiological auxin response in Arabidopsis plants. Additionally, the photoirradiation of DMPNB-caged auxin within a single cell can manipulate the intracellular auxin level and triggers auxin response. [source] Ontogeny of Plurihormonal Cells in the Anterior Pituitary of the Mouse, as Studied by Means of Hormone mRNA Detection in Single CellsJOURNAL OF NEUROENDOCRINOLOGY, Issue 8 2002E. Seuntjens Abstract The expression of mRNA of growth hormone (GH), prolactin (PRL), pro-opiomelanocortin (POMC) and the common glycoprotein hormone ,-subunit (,GSU) was studied by means of single cell reverse transcriptase-polymerase chain reaction in male mouse pituitary cells at key time points of fetal and postnatal development: embryonic day 16 (E16); postnatal day 1 (P1) and young-adult age (P38). At E16, the hormone mRNAs examined were detectable, although only in 44% of total cells. Most of the hormone-positive cells expressed only one of the tested hormone mRNAs (monohormonal) but 14% of them contained more than one hormone mRNA (plurihormonal cells). Combinations of GH mRNA with PRL mRNA, of ,GSU mRNA with GH and/or PRL mRNA and of POMC mRNA with GH and/or PRL mRNA or ,GSU mRNA were found. As expected, the proportion of hormone-positive cells rose as the mouse aged. The proportions of plurihormonal cells followed a developmental pattern independent of that of monohormonal cells and characteristic for each hormone mRNA examined. Cells coexpressing POMC mRNA with GH or PRL mRNA significantly rose in proportion between E16 and P1, while the proportion of cells coexpressing GH and PRL mRNA markedly increased between P1 and P38. The occurrence of cells displaying combined expression of ,GSU mRNA with GH and/or PRL mRNA did not significantly change during development. Remarkably, the population of cells expressing PRL mRNA only, was larger at E16 than at P1 and expanded again thereafter. In conclusion, the normal mouse pituitary develops a cell population that is capable of expressing multiple hormone mRNAs, thereby combining typical phenotypes of different cell lineages. These plurihormonal cells are already present during embryonic life. This population is of potential physiological relevance because development-related factors appear to determine which hormone mRNAs are preferentially coexpressed. Coexpression of multiple hormone mRNAs may represent a mechanism to respond to temporally increased endocrine demands. The data also suggest that the control of combined hormone expression is different from that of single hormone expression, raising questions about the current view on pituitary cell lineage specifications. [source] An In Vivo Fluorescent Sensor Reveals Intracellular Ins(1,3,4,5)P4 Dynamics in Single Cells,ANGEWANDTE CHEMIE, Issue 12 2010Reiko Sakaguchi Töte nicht den Boten! Ein optischer Sensor für D - myo -Inositol-1,3,4,5-tetrakisphosphat (Ins(1,3,4,5)P4), einen intrazellulären sekundären Botenstoff, resultiert beim Einbau eines Fluorophors in einen ausgewählten Cysteinrest einer Mutante der Pleckstrin-Homologie(PH)-Domäne des allgemeinen Phosphoinositidrezeptors,1 (GRP1). Der Biosensor visualisiert die Ins(1,3,4,5)P4 -Dynamik anhand der Agoniststimulierung in einzelnen lebenden Zellen. [source] Microfluidic Confinement of Single Cells of Bacteria in Small Volumes Initiates High-Density Behavior of Quorum Sensing and Growth and Reveals Its Variability,ANGEWANDTE CHEMIE, Issue 32 2009James Eine ist ein Quorum: Nur eine bis drei Zellen von Pseudomonas-aeruginosa -Bakterien können mithilfe der Mikrofluidik in kleinen Volumina eingegrenzt werden. Diese wenigen Zellen sind zum Quorum-Sensing (QS) befähigt und gehen QS-abhängiges Wachstum ein. Die Befunde ergaben auch, dass bei niedriger Zahl an Zellen das Auslösen von QS innerhalb einer Klonpopulation sehr variabel ist. [source] Single-cell gene profiling of planarian stem cells using fluorescent activated cell sorting and its "index sorting" function for stem cell researchDEVELOPMENT GROWTH & DIFFERENTIATION, Issue 1 2010Tetsutaro Hayashi To achieve an integrated understanding of the stem cell system of planarians at both the cellular and molecular levels, we developed a new method by combining "fluorescent activated cell sorting (FACS) index sorting" analysis and single-cell reverse transcription,polymerase chain reaction (RT,PCR) to detect the gene expression and cell cycle state of stem cells simultaneously. Single cells were collected using FACS, and cDNAs of each cell were used for semi-quantitative RT,PCR. The results were plotted on the FACS sorting profile using the "index sorting" function, which enabled us to analyze the gene expression in combination with cell biological data (such as cell cycle phase) for each cell. Here we investigated the adult stem cells of planarians using this method and obtained findings suggesting that the stem cells might undergo commitment during S to G2/M phase. This method could be a powerful and straightforward tool for examining the stem cell biology of not only planarians but also other organisms, including vertebrates. [source] Ultrastructural studies of midgut epithelium formation in Lepisma saccharina L. (Insecta, Zygentoma)JOURNAL OF MORPHOLOGY, Issue 3 2007M. M. Rost-Roszkowska Abstract At the end of embryogenesis of Lepisma saccharina L. (Insecta, Zygentoma), when the stomodaeum and proctodaeum are completely formed, the midgut epithelium is replaced by the primary midgut, a yolk mass is surrounded by a cell membrane. Midgut epithelium formation begins in the 1st larval stage. Energids migrate toward the yolk periphery and aggregate just beneath the cell membrane. They are gradually enclosed by cell membrane folds of the primary midgut. Single cells are formed. Succeeding energids join just formed cells. Thus, groups of cells, regenerative cell groups, are formed. Their number gradually increases. The external cells of the regenerative cell groups transform into epithelial cells and their basal regions spread toward the next regenerative cell groups. Epithelial cells of neighboring regenerative cell groups join each other to form the epithelium. At the end of the 2nd larval stage, just before molting, degeneration of newly the formed epithelium begins. Remains of organelles and basal membrane occur between the regenerative cell groups. The new epithelium is formed from the regenerative cell groups, which are now termed stem cells of the midgut epithelium. J. Morphol., 2007. © 2007 Wiley-Liss, Inc. [source] Analysis of amino acids in individual human erythrocytes by capillary electrophoresis with electroporation for intracellular derivatization and laser-induced fluorescence detectionELECTROPHORESIS, Issue 3 2004Hua Zhang Abstract A method for monitoring amino acids in single erythrocytes is described. For intracellular derivatization, reagent fluorescein isothiocyanate (FITC) was introduced into living cells by electroporation. For an 8 ,m erythrocyte, the analytes were diluted by a factor of only 1.6. After completion of the derivatization reaction, a single cell was injected into the separation capillary tip and lysed there. The derivatized amino acids were separated by capillary electrophoresis, followed by laser-induced fluorescence detection. Nine amino acids were quantitatively determined, with amounts of amino acids ranging from 3.8,32 amol/single cell. [source] Death and survival of heterozygous Lurcher Purkinje cells In vitroDEVELOPMENTAL NEUROBIOLOGY, Issue 8 2009Hadi S. Zanjani Abstract The differentiation and survival of heterozygous Lurcher (+/Lc) Purkinje cells in vitro was examined as a model system for studying how chronic ionic stress affects neuronal differentiation and survival. The Lurcher mutation in the ,2 glutamate receptor (GluR,2) converts an orphan receptor into a membrane channel that constitutively passes an inward cation current. In the GluR,2+/Lc mutant, Purkinje cell dendritic differentiation is disrupted and the cells degenerate following the first week of postnatal development. To determine if the GluR,2+/Lc Purkinje cell phenotype is recapitulated in vitro, +/+, and +/Lc Purkinje cells from postnatal Day 0 pups were grown in either isolated cell or cerebellar slice cultures. GluR,2+/+ and GluR,2+/Lc Purkinje cells appeared to develop normally through the first 7 days in vitro (DIV), but by 11 DIV GluR,2+/Lc Purkinje cells exhibited a significantly higher cation leak current. By 14 DIV, GluR,2+/Lc Purkinje cell dendrites were stunted and the number of surviving GluR,2+/Lc Purkinje cells was reduced by 75% compared to controls. However, treatment of +/Lc cerebellar cultures with 1-naphthyl acetyl spermine increased +/Lc Purkinje cell survival to wild type levels. These results support the conclusion that the Lurcher mutation in GluR,2 induces cell autonomous defects in differentiation and survival. The establishment of a tissue culture system for studying cell injury and death mechanisms in a relatively simple system like GluR,2+/Lc Purkinje cells will provide a valuable model for studying how the induction of a chronic inward cation current in a single cell type affects neuronal differentiation and survival. © 2009 Wiley Periodicals, Inc. Develop Neurobiol, 2009 [source] Mixed primary culture and clonal analysis provide evidence that NG2 proteoglycan-expressing cells after spinal cord injury are glial progenitorsDEVELOPMENTAL NEUROBIOLOGY, Issue 7 2007Soonmoon Yoo Abstract NG2+ cells in the adult rat spinal cord proliferate after spinal cord injury (SCI) and are postulated to differentiate into mature glia to replace some of those lost to injury. To further study these putative endogenous precursors, tissue at 3 days after SCI or from uninjured adults was dissociated, myelin partially removed and replicate cultures grown in serum-containing or serum-free medium with or without growth factors for up to 7 days in vitro (DIV). Cell yield after SCI was 5,6 times higher than from the normal adult. Most cells were OX42+ microglia/macrophages but there were also more than twice the normal number of NG2+ cells. Most of these coexpressed A2B5 or nestin, as would be expected for glial progenitors. Few cells initially expressed mature astrocyte (GFAP) or oligodendrocyte (CC1) markers, but more did at 7 DIV, suggesting differentiation of glial precursors in vitro. To test the hypothesis that NG2+ cells after SCI express progenitor-like properties, we prepared free-floating sphere and single cell cultures from purified suspension of NG2+ cells from injured spinal cord. We found that sphere cultures could be passaged in free-floating subcultures, and upon attachment the spheres clonally derived from an acutely purified single cell differentiated into oligodendrocytes and rarely astrocytes. Taken together, these data support the hypothesis that SCI stimulates proliferation of NG2+ cells that are glial progenitor cells. Better understanding the intrinsic properties of the NG2+ cells stimulated by SCI may permit future therapeutic manipulations to improve recovery after SCI. © 2007 Wiley Periodicals, Inc. Develop Neurobiol, 2007. [source] Fine-needle aspiration cytology of metastatic nasopharyngeal carcinomaDIAGNOSTIC CYTOPATHOLOGY, Issue 4 2005José M. Viguer M.D. Abstract Cytological features of nasopharyngeal carcinoma (NPC) were reviewed in an attempt to select cytological criteria that permit a specific recognition of metastases. For this purpose, 54 fine-needle aspiration (FNA) procedures from 43 patients with NPC were analyzed. Thirty-two (59.3%) procedures were performed before the histological diagnosis. In 25 (46.3%) procedures, smears showed many neoplastic single cells, clusters, and abundant lymphoid cells (mixed pattern). A dissociated (single cell) pattern consisting of individual neoplastic and lymphoid cells was seen in 18 (33.3%) cases. Finally, 11 (20.4%) cases showed cohesive epithelial clusters (cohesive pattern) without relevant cellular dissociation or lymphoid cells. Squamous-cell differentiation was seen in three of these cases. Most single neoplastic cells presented as large, pleomorphic naked nuclei. Other interesting findings were granulomas (n = 3), prominent eosinophilic infiltrates (n = 4), and suppurative changes (n = 5). In most smears with mixed and dissociated patterns, a nasopharyngeal origin could be suggested. On the contrary, those smears with a cohesive pattern were indistinguishable from other head and neck carcinomas. The presence (on cervical lymph nodes) of a dissociated or mixed (single cells and groups) architectural pattern of large, anaplastic cells and naked nuclei accompanied by an abundant lymphoid component is highly suggestive of undifferentiated NPC. Cytology offers a rapid diagnosis, establishes the necessity of a complete cavum examination, and helps in avoiding unnecessary and harmful biopsies. Diagn. Cytopathol. 2005;32:233,237. © 2005 Wiley-Liss, Inc. [source] CE analysis of the acidic organelles of a single cellELECTROPHORESIS, Issue 14 2007Yun Chen Abstract The properties of organelles within a cell have been shown to be highly heterogeneous. Until now, it has been unclear just how much of this heterogeneity is endemic to the organelle subpopulations themselves and how much is actually due to stochastic cellular noise. An attractive approach for investigating the origins of heterogeneity among the organelles of a single cell is CE with LIF detection (CE-LIF). As a proof of principle, in this report we optimize and use a single cell CE-LIF method to investigate the properties of endocytic (acidic) organelles. Our results show that the properties of individual acidic organelles containing Alexa Fluor® 488 Dextran suggest that there are two groups of CCRF-CEM cells: a group with a high dextran content per cell, and a group with a low dextran content per cell. Furthermore, the individual organelle measurements of the single cells allow us to compare in each group the distributions of doxorubicin content per acidic organelle and electrophoretic mobilities of these organelles. [source] Analysis of amino acids in individual human erythrocytes by capillary electrophoresis with electroporation for intracellular derivatization and laser-induced fluorescence detectionELECTROPHORESIS, Issue 3 2004Hua Zhang Abstract A method for monitoring amino acids in single erythrocytes is described. For intracellular derivatization, reagent fluorescein isothiocyanate (FITC) was introduced into living cells by electroporation. For an 8 ,m erythrocyte, the analytes were diluted by a factor of only 1.6. After completion of the derivatization reaction, a single cell was injected into the separation capillary tip and lysed there. The derivatized amino acids were separated by capillary electrophoresis, followed by laser-induced fluorescence detection. Nine amino acids were quantitatively determined, with amounts of amino acids ranging from 3.8,32 amol/single cell. [source] Exploration of the functional hierarchy of the basal layer of human epidermis at the single-cell level using parallel clonal microcultures of keratinocytesEXPERIMENTAL DERMATOLOGY, Issue 4 2010Nicolas O. Fortunel Please cite this paper as: Exploration of the functional hierarchy of the basal layer of human epidermis at the single-cell level using parallel clonal microcultures of keratinocytes. Experimental Dermatology 2010. Abstract:, The basal layer of human epidermis contains both stem cells and keratinocyte progenitors. Because of this cellular heterogeneity, the development of methods suitable for investigations at a clonal level is dramatically needed. Here, we describe a new method that allows multi-parallel clonal cultures of basal keratinocytes. Immediately after extraction from tissue samples, cells are sorted by flow cytometry based on their high integrin-,6 expression and plated individually in microculture wells. This automated cell deposition process enables large-scale characterization of primary clonogenic capacities. The resulting clonal growth profile provided a precise assessment of basal keratinocyte hierarchy, as the size distribution of 14-day-old clones ranged from abortive to highly proliferative clones containing 1.7 × 105 keratinocytes (17.4 cell doublings). Importantly, these 14-day-old primary clones could be used to generate three-dimensional reconstructed epidermis with the progeny of a single cell. In long-term cultures, a fraction of highly proliferative clones could sustain extensive expansion of >100 population doublings over 14 weeks and exhibited long-term epidermis reconstruction potency, thus fulfilling candidate stem cell functional criteria. In summary, parallel clonal microcultures provide a relevant model for single-cell studies on interfollicular keratinocytes, which could be also used in other epithelial models, including hair follicle and cornea. The data obtained using this system support the hierarchical model of basal keratinocyte organization in human interfollicular epidermis. [source] A gene duplication led to specialized ,-aminobutyrate and ,-alanine aminotransferase in yeastFEBS JOURNAL, Issue 7 2007Gorm Andersen In humans, ,-alanine (BAL) and the neurotransmitter ,-aminobutyrate (GABA) are transaminated by a single aminotransferase enzyme. Apparently, yeast originally also had a single enzyme, but the corresponding gene was duplicated in the Saccharomyces kluyveri lineage. SkUGA1 encodes a homologue of Saccharomyces cerevisiae GABA aminotransferase, and SkPYD4 encodes an enzyme involved in both BAL and GABA transamination. SkPYD4 and SkUGA1 as well as S. cerevisiaeUGA1 and Schizosaccharomyces pombeUGA1 were subcloned, over-expressed and purified. One discontinuous and two continuous coupled assays were used to characterize the substrate specificity and kinetic parameters of the four enzymes. It was found that the cofactor pyridoxal 5,-phosphate is needed for enzymatic activity and ,-ketoglutarate, and not pyruvate, as the amino group acceptor. SkPyd4p preferentially uses BAL as the amino group donor (Vmax/Km = 0.78 U·mg,1·mm,1), but can also use GABA (Vmax/Km = 0.42 U·mg,1·mm,1), while SkUga1p only uses GABA (Vmax/Km = 4.01 U·mg,1·mm,1). SpUga1p and ScUga1p transaminate only GABA and not BAL. While mammals degrade BAL and GABA with only one enzyme, but in different tissues, S. kluyveri and related yeasts have two different genes/enzymes to apparently ,distinguish' between the two reactions in a single cell. It is likely that upon duplication ,200 million years ago, a specialized Uga1p evolved into a ,novel' transaminase enzyme with broader substrate specificity. [source] Development of a Direct Alcohol Alkaline Fuel Cell StackFUEL CELLS, Issue 4 2010D. Gaurava Abstract Direct alcohol alkaline fuel cells (DAAFC) are one of the potential fuel cell types in the category of low temperature fuel cells, which could become an energy source for portable electronic equipment in future. In the present study, a simple DAAFC stack has been developed and studied to evaluate the maximum performance for a given fuel (methanol or ethanol) and electrolyte (KOH) at various concentrations and temperatures. The open circuit voltage of the stack of four cells was nearly 4.0,V. A particular combination, 2,M fuel (methanol or ethanol) and 3,M KOH, results in maximum power density of the stack. The maximum power density obtained from the DAAFC stack (25,°C) was 50,mW,cm,2 at 20,mA,cm,2 for methanol and 17,mA,cm,2 for ethanol. The stack power density corroborated with that obtained from a single cell, indicating there was no further loss in the stack. [source] Optimisation and Evaluation of La0.6Sr0.4CoO3,,,, Cathode for Intermediate Temperature Solid Oxide Fuel CellsFUEL CELLS, Issue 5 2009Youkun Tao Abstract In this work, La0.6Sr0.4CoO3,,,,/Ce1,,xGdxO2,,,, (LSC/GDC) composite cathodes are investigated for SOFC application at intermediate temperatures, especially below 700,°C. The symmetrical cells are prepared by spraying LSC/GDC composite cathodes on a GDC tape, and the lowest polarisation resistance (Rp) of 0.11,,,cm2 at 700,°C is obtained for the cathode containing 30,wt.-% GDC. For the application on YSZ electrolyte, symmetrical LSC cathodes are fabricated on a YSZ tape coated on a GDC interlayer. The impact of the sintering temperature on the microstructure and electrochemical properties is investigated. The optimum temperature is determined to be 950,°C; the corresponding Rp of 0.24,,,cm2 at 600,°C and 0.06,,,cm2 at 700,°C are achieved, respectively. An YSZ-based anode-supported solid oxide fuel cell is fabricated by employing LSC/GDC composite cathode sintered at 950,°C. The cell with an active electrode area of 4,×,4,cm2 exhibits the maximum power density of 0.42,W,cm,2 at 650,°C and 0.54,W,cm,2 at 700,°C. More than 300,h operating at 650,°C is carried out for an estimate of performance and degradation of a single cell. Despite a decline at the beginning, the stable performance during the later term suggests a potential application. [source] A Hybrid Finite-Difference and Analytic Element Groundwater ModelGROUND WATER, Issue 4 2010H.M. Haitjema Regional finite-difference models tend to have large cell sizes, often on the order of 1,2 km on a side. Although the regional flow patterns in deeper formations may be adequately represented by such a model, the intricate surface water and groundwater interactions in the shallower layers are not. Several stream reaches and nearby wells may occur in a single cell, precluding any meaningful modeling of the surface water and groundwater interactions between the individual features. We propose to replace the upper MODFLOW layer or layers, in which the surface water and groundwater interactions occur, by an analytic element model (GFLOW) that does not employ a model grid; instead, it represents wells and surface waters directly by the use of point-sinks and line-sinks. For many practical cases it suffices to provide GFLOW with the vertical leakage rates calculated in the original coarse MODFLOW model in order to obtain a good representation of surface water and groundwater interactions. However, when the combined transmissivities in the deeper (MODFLOW) layers dominate, the accuracy of the GFLOW solution diminishes. For those cases, an iterative coupling procedure, whereby the leakages between the GFLOW and MODFLOW model are updated, appreciably improves the overall solution, albeit at considerable computational cost. The coupled GFLOW,MODFLOW model is applicable to relatively large areas, in many cases to the entire model domain, thus forming an attractive alternative to local grid refinement or inset models. [source] Theta rhythm of navigation: Link between path integration and landmark navigation, episodic and semantic memoryHIPPOCAMPUS, Issue 7 2005György Buzsáki Abstract Five key topics have been reverberating in hippocampal-entorhinal cortex (EC) research over the past five decades: episodic and semantic memory, path integration ("dead reckoning") and landmark ("map") navigation, and theta oscillation. We suggest that the systematic relations between single cell discharge and the activity of neuronal ensembles reflected in local field theta oscillations provide a useful insight into the relationship among these terms. In rats trained to run in direction-guided (1-dimensional) tasks, hippocampal cell assemblies discharge sequentially, with different assemblies active on opposite runs, i.e., place cells are unidirectional. Such tasks do not require map representation and are formally identical with learning sequentially occurring items in an episode. Hebbian plasticity, acting within the temporal window of the theta cycle, converts the travel distances into synaptic strengths between the sequentially activated and unidirectionally connected assemblies. In contrast, place representations by hippocampal neurons in 2-dimensional environments are typically omnidirectional, characteristic of a map. Generation of a map requires exploration, essentially a dead reckoning behavior. We suggest that omnidirectional navigation through the same places (junctions) during exploration gives rise to omnidirectional place cells and, consequently, maps free of temporal context. Analogously, multiple crossings of common junction(s) of episodes convert the common junction(s) into context-free or semantic memory. Theta oscillation can hence be conceived as the navigation rhythm through both physical and mnemonic space, facilitating the formation of maps and episodic/semantic memories. © 2005 Wiley-Liss, Inc. [source] Mast cells and eicosanoid mediators: a system of reciprocal paracrine and autocrine regulationIMMUNOLOGICAL REVIEWS, Issue 1 2007Joshua A. Boyce Summary:, When activated by specific antigen, complement, or other transmembrane stimuli, mast cells (MCs) generate three eicosanoids: prostaglandin (PG)D2, leukotriene (LT)B4, and LTC4, the parent molecule of the cysteinyl leukotrienes (cysLTs). These diverse lipid mediators, which are generated from a single cell membrane-associated precursor, arachidonic acid, can initiate, amplify, or dampen inflammatory responses and influence the magnitude, duration, and nature of subsequent immune responses. PGD2 and cysLTs, which were originally recognized for their bronchoconstricting and vasoactive properties, also serve diverse and pivotal functions in effector cell trafficking, antigen presentation, leukocyte activation, matrix deposition, and fibrosis. LTB4 is a powerful chemoattractant for neutrophils and certain lymphocyte subsets. Thus, MCs can contribute to each of these processes through eicosanoid generation. Additionally, MCs express G-protein-coupled receptors specific for cysLTs, LTB4, and another eicosanoid, PGE2. Each of these receptors can regulate MC functions in vivo by autocrine and paracrine mechanisms. This review focuses on the biologic functions for MC-associated eicosanoids, the regulation of their production, and the mechanisms by which eicosanoids may regulate MC function in host defense and disease. [source] Heterogeneous traffic flow modelling for an arterial using grid based approachJOURNAL OF ADVANCED TRANSPORTATION, Issue 4 2008P. J. Gundaliya Abstract A grid based modelling approach akin to cellular automata (CA) is adopted for heterogeneous traffic flow simulation. The road space is divided into a grid of equally sized cells. Moreover, each vehicle type occupies one or more cell as per its size unlike CA traffic flow model where each vehicle is represented by a single cell. Model needs inputs such as vehicle size, its maximum speed, acceleration, deceleration, probability constants, and arrival pattern. The position and speed of the vehicles are assumed to be discrete. The speed of each vehicle changes according to its interactions with other vehicles, following some stochastic rules depending on the circumstances. The model is calibrated and validated using real data and VISSIM. The results indicate that grid based model can reasonably well simulate complex heterogeneous traffic as well as offers higher computational efficiency needed for real time application. [source] Dual Mechanism of Intercellular Communication in HOBIT Osteoblastic Cells: A Role for Gap-Junctional HemichannelsJOURNAL OF BONE AND MINERAL RESEARCH, Issue 8 2001Milena Romanello Abstract Intercellular communication allows tissue coordination of cell metabolism and sensitivity to extracellular stimuli. Paracrine stimulation and cell-to-cell coupling through gap junctions induce the formation of complex cellular networks, which favors the intercellular exchange of nutrients and second messengers. Intercellular Ca2+ signaling was investigated in human osteoblast-like initial transfectant (HOBIT) cells, a human osteoblastic cell line in which cells retain most of the osteoblastic differentiation markers. HOBIT cells express connexin43 (Cx43) clustered at the cell-to-cell boundary and display functional intercellular coupling as assessed by the intercellular transfer of Lucifer yellow. Mechanical stimulation of a single cell induced a wave of increased Ca2+ that was radially propagated to surrounding cells. Treatment of cells with thapsigargin blocked mechanically induced signal propagation. Intercellular Ca2+ spreading and dye transfer were inhibited by 18,-glycyrrhetinic acid (18-GA), showing the involvement of gap junctions in signal propagation. Pretreatment of cells with suramin or with apyrase decreased the extent of wave propagation, suggesting that ATP-mediated paracrine stimulation contribute to cell-to-cell signaling. The functional expression of gap-junctional hemichannels was evidenced in experiments of Mn2+ quenching, extracellular dye uptake, and intracellular Ca2+ release, activated by uptake of inositol 1,4,5-trisphosphate (InsP3) from the external medium. Gap-junctional hemichannels were activated by low extracellular Ca2+ concentrations and inhibited by 18-GA. A role for Cx hemichannels in adenosine triphosphate (ATP) release and paracrine stimulation is suggested. [source] Epigenetic pre-patterning and dynamics during initial stages of mammalian preimplantation developmentJOURNAL OF CELLULAR PHYSIOLOGY, Issue 2 2010Theodore P. Rasmussen Mammals, like all multicellular organisms, develop from a single cell,the totipotent zygote. During preimplantation development and subsequent development in utero, over 200 distinct cell types are established and integrated into the organ systems and tissues of the developing organism. Much of the field of mammalian developmental biology is devoted to investigation of mechanisms that govern the formation of complete organs and tissues. In contrast to later development, which consumes the vast majority of time associated with development in utero, preimplantation development and germ layer specification occur rapidly. Yet knowledge is limited regarding the regulatory mechanisms that specify the transient, but pluripotent, cellular lineages that form during the initial stages of mammalian development. Gametogenesis and preimplantation development are marked by dramatic and pervasive epigenetic changes rooted in chromatin dynamics. The fundamental mechanisms that specify subsequent cellular lineages of the conceptus are only now becoming understood, and tend to rely relatively heavily upon broad epigenetic mechanisms in addition to master transcription factors. This review considers epigenetic regulation in the very earliest stages of preimplantation development. In addition, recent advances which indicate that some epigenetic coding is imposed during gametogenesis and maintained during preimplantation development are considered. J. Cell. Physiol. 225: 333,336, 2010. © 2010 Wiley-Liss, Inc. [source] Molecular and Biochemical Evidence for Phenylpropanoid Synthesis and Presence of Wall-linked Phenolics in Cotton FibersJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 7 2009Ling Fan Abstract The mature cotton (Gossypium hirsutum L.) fiber is a single cell with a typically thickened secondary cell wall. The aim of this research was to use molecular, spectroscopic and chemical techniques to investigate the possible occurrence of previously overlooked accumulation of phenolics during secondary cell wall formation in cotton fibers. Relative quantitative reverse transcription-polymerase chain reaction analysis showed that GhCAD6 and GhCAD1 were predominantly expressed among seven gene homologs, only GhCAD6 was up-regulated during secondary wall formation in cotton fibers. Phylogenic analysis revealed that GhCAD6 belonged to Class I and was proposed to have a major role in monolignol biosynthesis, and GhCAD1 belonged to Class III and was proposed to have a compensatory mechanism for monolignol biosynthesis. Amino acid sequence comparison showed that the cofactor binding sites of GhCADs were highly conserved with high similarity and identity to bona fide cinnamyl alcohol dehydrogenases. The substrate binding site of GhCAD1 is different from GhCAD6. This difference was confirmed by the different catalytic activities observed with the enzymes. Cell wall auto-fluorescence, Fourier transform infrared spectroscopy (FTIR), high-performance liquid chromatography (HPLC) and chemical analyses confirmed that phenolic compounds were bound to the cell walls of mature cotton fibers. Our findings may suggest a potential for genetic manipulation of cotton fiber properties, which are of central importance to agricultural, cotton processing and textile industries. [source] An increase in intracellular free calcium ions by nicotinic acetylcholine receptors in a single cultured rat cortical astrocyteJOURNAL OF NEUROSCIENCE RESEARCH, Issue 4 2005Hirotaka Oikawa Abstract Neuronal nicotinic acetylcholine receptors (nAChRs) are composed of an assembly between at least seven alpha (,2,,7, ,9) and three beta (,2,,4) subunits in mammals. The addition of 50 mM KCl or 1 mM nicotine immediately increased the number of cells with high fluorescence intensity in rat cortical astrocytes on fluo-3 fluorescence measurement. Nicotine was effective at increasing the fluorescence intensity in astrocytes cultured for 2 days after replating, but not in those used 1 or 5 days after replating, without markedly affecting the cellular viability irrespective of the exposure period. Nicotine markedly increased the fluorescence intensity in a concentration-dependent manner at a concentration range of 10,100 ,M in cultured astrocytes when analyzed on a responsive single cell. In these responsive single cells, the increase by nicotine was significantly prevented by the heteromeric ,4/,2 subtype antagonist dihydro-,-erythroidine and the homomeric ,7 subtype antagonist methyllycaconitine, as well as by nifedipine and EGTA but not thapsigargin. Methyllycaconitine failed to inhibit further the increase by nicotine in the presence of nifedipine, however, whereas the expression of mRNA was seen for all mammalian neuronal nAChR subunits in cultured rat cortical astrocytes as well as neurons. These results suggest that nicotine may increase intracellular free Ca2+ through the influx of extracellular Ca2+ across L-type voltage-gated Ca2+ channels rather than Ca2+ release from intracellular stores, in a manner related to the ,4/,2 and/or ,7 nAChR channels functionally expressed in cultured rat cortical astrocytes. © 2005 Wiley-Liss, Inc. [source] Simultaneous Raman micro,spectroscopy of optically trapped and stacked cellsJOURNAL OF RAMAN SPECTROSCOPY, Issue 9 2007P. R. T. Jess Abstract The combination of Raman spectroscopy and optical trapping holds great promise for single-cell studies and is an emergent theme in microfluidic environments. Here, the evolution of the Raman signal intensity with an axial increment of the mass of the substance of interest inside a specific Raman excitation volume is investigated. Whilst Raman spectroscopy may be applied to tissue samples, solutions and single cells, there are no easily available methods to rapidly acquire signals from small cell populations. We show a simple but powerful method to record the Raman intensity signal simultaneously from a small number of trapped cells or colloidal particles using the technique of optical stacking. The Raman spectra of stacks of red blood cells and yeast cells show that this method can be applied to biological systems. We demonstrate how we may reveal biochemical fingerprints that would otherwise require long integration times for each single cell or averaging over many sequentially acquired cell spectra. There is potential to apply this method to directly attain Raman spectra from sorted sub-populations of normal, abnormal and tumour cell lines. Copyright © 2007 John Wiley & Sons, Ltd. [source] Raman spectroscopic signature of life in a living yeast cellJOURNAL OF RAMAN SPECTROSCOPY, Issue 7 2004Yu-San Huang Abstract We have discovered a Raman spectroscopic signature that sharply reflects the metabolic activity of a mitochondrion in a living yeast cell. Raman mapping experiments on a GFP-labeled yeast cell showed that this signature originated exclusively from mitochondria. Addition of KCN caused a rapid decrease and subsequent disappearance of the signature followed by gradual changes of the phospholipid Raman bands, indicating that respiration was first inhibited by KCN and then lowered metabolic activity gradually deteriorated the double-membrane structure of a mitochondrion. We can now monitor the life and death of a single cell by time- and space-resolved Raman spectroscopy. Copyright © 2004 John Wiley & Sons, Ltd. [source] Expression of an artificial polypeptide with a repeated tripeptide glutamyl,tryptophanyl,lysine in Saccharomyces cerevisiaeLETTERS IN APPLIED MICROBIOLOGY, Issue 2 2003S.Y. Lee Abstract Aims: Artificial genes, which encode 48 or 64 repeats of a tripeptide, glutamyl,tryptophanyl,lysine have been cloned to the yeast expression vector pAM82 containing the PHO5 promoter and expressed in Saccharomyces cerevisiae AH22. Methods and Results: When the yeast cells harbouring recombinant plasmids pALTG6-2 and pALTG4-4 were derepressed in Burkholder minimal medium (Toh-e, A., Ueda, Y., Kakimoto, S.I. and Oshima, Y. (1973) Journal of Bacteriology113, 727,738) containing low phosphate (0·03 g l,1 KH2PO4 and 1·5 g l,1 KCl), the expression was the highest after 24 h induction and the artificial polypeptides were synthesized to about 10% (pALTG6-2) and 14% (pALTG4-4) of the total cell protein. Conclusions: The artificial polypeptides produced in yeast were made to react with the rabbit antiserum against the polypeptide purified from Escherichia coli and found only in the pellet fraction of cell lysates, indicating the formation of inclusion body. Artificial polypeptide consisting of Glu,Trp,Lys may be useful as partial supplement in food and feeds. Significance and Impact of the Study: The production of single cell enriched with homopolymers of an essential amino acid in yeast might be an important tool of supplementing cereal diets and feed grain rations and could be used as means for improvement of the amino acid profile of single cell protein and production of pharmaceutical peptides. [source] Fabrication of high performance 3C-SiC vertical MOSFETs by reducing planar defectsPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 7 2008Hiroyuki Nagasawa Abstract The planar defect density of 3C-SiC can be reduced by growing it on undulant-Si substrates. However, specific stacking faults (SFs) remain, that expose the Si-face on the (001) surface. These residual SFs increase the leakage current in devices made with 3C-SiC. They can be eliminated using an advanced SF-reduction method called switch-back epitaxy (SBE) that combines polarity conversion with homoepitaxial growth. Vertical metal,oxide,semiconductor field-effect-transistors (MOSFETs) are fabricated on 3C-SiC with SBE, varying in size from a single cell with an area of (30 × 30) ,m2 to 12,000 hexagonal cells on a (3 × 3) mm2 chip. The MOSFET characteristics suggest that currents greater than 100 A are realistic for blocking voltages of 600,1,200 V by increasing the number of cells with reduced cell-pitch. The combination of blocking voltage capability with a demonstrable high current capacity shows that 3C-SiC is well-suited for use in vertical MOSFETs for high- and medium-power electronic applications. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Whole genome amplification from a single cell: a new era for preimplantation genetic diagnosisPRENATAL DIAGNOSIS, Issue 4 2007Serdar Coskun Abstract Preimplantation genetic diagnosis (PGD) is a technique used for determining the genetic status of a single cell biopsied from embryos or oocytes. Genetic analysis from a single cell is both rewarding and challenging, especially in PGD. The starting material is very limited and not replaceable, and the diagnosis has to be made in a very short time. Different whole genome amplification (WGA) techniques have been developed to specifically increase the DNA quantities originating from clinical samples with limited DNA contents. In this review, currently available WGA techniques are introduced and, among them, multiple displacement amplification (MDA) is discussed in detail. MDA generates abundant assay-ready DNA to perform broad panels of genetic assays through its ability to rapidly amplify genomes from single cells. The utilization of MDA for single-cell molecular analysis is expanding at a high rate, and MDA is expected to soon become an integral part of PGD. Copyright © 2007 John Wiley & Sons, Ltd. [source] | ||||||||||||||||||||||||||||||||||||||||||||||