985 resultados para cell location


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A local algorithm with local horizon r is a distributed algorithm that runs in r synchronous communication rounds; here r is a constant that does not depend on the size of the network. As a consequence, the output of a node in a local algorithm only depends on the input within r hops from the node. We give tight bounds on the local horizon for a class of local algorithms for combinatorial problems on unit-disk graphs (UDGs). Most of our bounds are due to a refined analysis of existing approaches, while others are obtained by suggesting new algorithms. The algorithms we consider are based on network decompositions guided by a rectangular tiling of the plane. The algorithms are applied to matching, independent set, graph colouring, vertex cover, and dominating set. We also study local algorithms on quasi-UDGs, which are a popular generalisation of UDGs, aimed at more realistic modelling of communication between the network nodes. Analysing the local algorithms on quasi-UDGs allows one to assume that the nodes know their coordinates only approximately, up to an additive error. Despite the localisation error, the quality of the solution to problems on quasi-UDGs remains the same as for the case of UDGs with perfect location awareness. We analyse the increase in the local horizon that comes along with moving from UDGs to quasi-UDGs.

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A specific membrane receptor for plasma retinol-binding protein has been demonstrated in testicular cells. Prealbumin-2 did not show any specific binding to the membrane. The affinity of retinol-binding protein for receptor drastically decreases upon delivery of retinol and the retinol-binding protein does not enter the cell. The mechanism of delivery of retinol to the target cell by plasma retinol-binding protein has been investigated. The process involves two steps: direct binding of retinol-binding protein to the receptor and uptake of retinol by the target cell with a concomitant drastic reduction in the affinity of the retinol-binding protein to the receptor. Probably the second step of the process needs a cytosolic factor, possibly the cellular retinol-binding protein or an enzyme.The binding of retinol-binding protein to the receptor is saturable and reverible. The interaction shows a Kd value of 2.1 · 10âˆ10 M. The specific binding of a retinol-binding protein with great affinity has been employed in the development of a method for radioassay of the receptor. The receptor level of the gonadal cell has been found to vary with the stage of differentiation. The receptor concentrations in 11-week-old birds and adult birds are comparable. Testoterone treatment of 11-week-old birds produced a substantial increase in the receptor concentration over control, while the protein content increased marginally, indicating that, probably, synthesis of the receptor is specifically induced by testoterone during spermatogenesis, and the concentration of receptor is relatively higher before the formation of the acrosome.

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Catalytic combustion of H-2 was carried out over combustion synthesized noble metal (Pd or Pt) ion-substituted CeO2 based catalysts using a feed stream that simulated exhaust gases from a fuel cell processor The catalysts showed a high activity for H-2-combustion and complete conversion was achieved below 200 C over all the catalysts when O-2 was used in a stoichiometric amount With higher amounts of O-2 the reaction rates Increased and complete conversions were possible below 100 C The reaction was also carried out over Pd-impregnated CeO2 The conversions of H-2 with stoichiometric amount of O-2 were found to be higher over Pd-substituted compound The mechanism of the reaction over noble metal-substituted compounds was proposed on the basis of X-ray photoelectron spectroscopy studies The redox couples between Ce and metal ions were established and a dual site redox mechanism was pi posed for the reaction (C) 2010 Elsevier B V All rights reserved

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Lamb-wave-based damage detection methods using the triangulation technique are not suitable for handling structures with complex shapes and discontinuities as the parametric/analytical representation of these structures is very difficult. The geodesic concept is used along with the triangulation technique to overcome the above problem. The present work is based on the fundamental fact that a wave takes the minimum energy path to travel between two points on any multiply connected surface and this reduces to the shortest distance path or geodesic. The geodesics are computed on the meshed surface of the structure using the fast marching method. The wave response matrix of the given sensor configuration for the healthy and the damaged structure is obtained experimentally. The healthy and damage response matrices are compared and their difference gives the time information about the reflection of waves from the damage. A wavelet transform is used to extract the arrival time information of the wave scattered by the damage from the acquired Lamb wave signals. The computed geodesics and time information are used in the ellipse algorithm of triangulation formulation to locate the loci of possible damage location points for each actuator-sensor pair. The results obtained for all actuator-sensor pairs are combined and the intersection of multiple loci gives the damage location result. Experiments were conducted in aluminum and composite plate specimens to validate this method.

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Thunderstorm is a dangerous electrical phenomena in the atmosphere. Thundercloud is formed when thermal energy is transported rapidly upwards in convective updraughts. Electrification occurs in the collisions of cloud particles in the strong updraught. When the amount of charge in the cloud is large enough, electrical breakdown, better known as a flash, occurs. Lightning location is nowadays an essential tool for the detection of severe weather. Located flashes indicate in real time the movement of hazardous areas and the intensity of lightning activity. Also, an estimate for the flash peak current can be determined. The observations can be used in damage surveys. The most simple way to represent lightning data is to plot the locations on a map, but the data can be processed in more complex end-products and exploited in data fusion. Lightning data serves as an important tool also in the research of lightning-related phenomena, such as Transient Luminous Events. Most of the global thunderstorms occur in areas with plenty of heat, moisture and tropospheric instability, for example in the tropical land areas. In higher latitudes like in Finland, the thunderstorm season is practically restricted to the summer season. Particular feature of the high-latitude climatology is the large annual variation, which regards also thunderstorms. Knowing the performance of any measuring device is important because it affects the accuracy of the end-products. In lightning location systems, the detection efficiency means the ratio between located and actually occurred flashes. Because in practice it is impossible to know the true number of actually occurred flashes, the detection efficiency has to be esimated with theoretical methods.

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Abrin is a type II ribosome-inactivating protein comprising of two subunits, A and B. Of the two, the A-subunit harbours the RNA-N-glycosidase activity and the B subunit is a galactose specific lectin that enables the entry of the protein inside the cell. Abrin inhibits protein synthesis and has been reported to induce apoptosis in several cell types. Based on these observations abrin is considered to have potential for the construction of immunotoxin in cell targeted therapy. Preliminary data from our laboratory however showed that although abrin inhibited the protein synthesis in all cell types, the mode of cell death varied. The aim of the present study was therefore to understand different death pathways induced by abrin in different cells. We used the human B cell line, U266B1 and compared it with the earlier studied T cell line Jurkat, for abrin-mediated inhibition of protein translation as well as cell death. While abrin triggered programmed apoptosis in Jurkat cells in a caspase-dependent manner, it induced programmed necrosis in U266B1 cells in a caspase-independent manner, even when there was reactive oxygen species production and loss of mitochondrial membrane potential. The data revealed that abrin-mediated necrosis involves lysosomal membrane permeabilization and release of cathepsins from the lysosomes. Importantly, the choice of abrin-mediated death pathway in the cells appears to depend on which of the two events occurs first: lysosomal membrane permeabilization or loss of mitochondrial membrane potential that decides cell death by necrosis or apoptosis. (C) 2010 Elsevier Ltd. All rights reserved.

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The identification of small molecules that affect T cell activation is an important area of research. Three molecules that regulate plant growth and differentiation, but not their structurally similar analogs, were identified to enhance primary mouse CD4(+) T cell activation in conjunction with soluble anti-CD3 stimulation: Indoleacetic acid (natural plant auxin), 1-Napthaleneacetic acid (synthetic plant auxin) and 2,4-Dichlorophenoxyacetic acid (synthetic plant auxin and herbicide). These effects are distinct in comparison to Curcumin, the well known phenolic immunomodulator, which lowers T cell activation. An investigation into the mechanisms of action of the three plant growth regulators revealed a rapid induction of reactive oxygen species (ROS), mainly comprising H2O2 . In addition, these three molecules synergize with soluble anti-CD3 signaling to enhance intracellular Ca2+ concentrations Ca2+](i), leading to greater T cell activation, e.g. induction of CD25 and IL-2. Enhanced production of TNF alpha and IFN gamma by CD4+ T cells is also observed upon plant growth regulator treatment with soluble anti-CD3. Interestingly, maximal IL-2 production and CD4(+) T cell cycle progression are observed upon activation with soluble anti-CD3 and phorbol 12-myristate 13-acetate (PMA), a phorbol ester. Additionally, stimulation with PMA and Ionomcyin (a Ca2+ ionophore), which activates T cells by circumventing the TCR, and plant growth regulators also demonstrated the role of the strength of signal (SOS): T cell cycle progression is enhanced with gentle activation conditions but decreased with strong activation conditions. This study demonstrates the direct effects of three plant growth regulators on CD4(+) T cell activation and cycling. (C) 2010 Elsevier B.V. All rights reserved.

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The radiative impact of aerosols is one of the largest sources of uncertainty in estimating anthropogenic climate perturbations. Here we have used independent ground-based radiometer measurements made simultaneously with comprehensive measurements of aerosol microphysical and optical properties at a highly populated urban site, Bangalore (13.02 degrees N, 77.6 degrees E) in southern India during a dedicated campaign during winter of 2004 and summer and pre-monsoon season of 2005. We have also used longer term measurements carried out at this site to present general features of aerosols over this region. The aerosol radiative impact assessments were made from direct measurements of ground reaching irradiance as well as by incorporating measured aerosol properties into a radiative transfer model. Large discrepancies were observed between measured and modeled (using radiative transfer models, which employed measured aerosol properties) radiative impacts. It appears that the presence of elevated aerosol layers and (or) inappropriate description of aerosol state of mixing are (is) responsible for the discrepancies. On a monthly scale reduction of surface irradiance due to the presence of aerosols (estimated using radiative flux measurements) varies from 30 to 65 W m(-2). The lowest values in surface radiative impact were observed during June when there is large reduction in aerosol as a consequence of monsoon rainfall. Large increase in aerosol-induced surface radiative impact was observed from winter to summer. Our investigations re-iterate the inadequacy of aerosol measurements at the surface alone and importance of representing column properties (using vertical profiles) accurately in order to assess aerosol-induced climate changes accurately. (C) 2010 Elsevier Ltd. All rights reserved.

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A series of isomeric cationic surfactants (S1-S5) bearing a long alkyl chain that carries a 1,4-phenylene unit and a trimethyl ammonium headgroup was synthesized; the location of the phenyl ring within the alkyl tail was varied in an effort to understand its influence on the amphiphilic properties of the surfactants. The cmc's of the surfactants were estimated using ionic conductivity measurements and isothermal calorimetric titrations (ITC); the values obtained by the two methods were found to be in excellent agreement. The ITC measurements provided additional insight into the various thermodynamic parameters associated with the micellization process. Although all five surfactants have exactly the same molecular formula, their micellar properties were seen to vary dramatically depending on the location of the phenyl ring; the cmc was seen to decrease by almost an order of magnitude when the phenyl ring was moved from the tail end (cmc of S1 is 23 mM) to the headgroup region (cmc of S5 is 3 mM). In all cases, the enthalpy of micellization was negative but the entropy of micellization was positive, suggesting that in all of these systems the formation of micelles is both enthalpically and entropically favored. As expected, the decrease in cmc values upon moving the phenyl ring from the tail end to he headgroup region is accompanied by an increase in the thermodynamic driving force (Delta G) for micellization. To understand further the differences in the micellar structure of these surfactants, small-angle neutron scattering (SANS) measurements were carried out; these measurements reveal that the aggregation number of the micelles increases as the cmc decreases. This increase in the aggregation number is also accompanied by an increase in the asphericity of the micellar aggregate and a decrease in the fractional charge. Geometric packing arguments are presented to account for these changes in aggregation behavior as a function of phenyl ring location.

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We present results from numerical simulations using a â˜â˜cell-dynamical systemââ to obtain solutions to the time-dependent Ginzburg-Landau equation for a scalar, two-dimensional (2D), (Φ2)2 model in the presence of a sinusoidal external magnetic field. Our results confirm a recent scaling law proposed by Rao, Krishnamurthy, and Pandit [Phys. Rev. B 42, 856 (1990)], and are also in excellent agreement with recent Monte Carlo simulations of hysteretic behavior of 2D Ising spins by Lo and Pelcovits [Phys. Rev. A 42, 7471 (1990)].

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Chronic myeloid leukemia (CML) is one of the most studied human malignancies. It is caused by an autonomously active tyrosine kinase BCR-ABL, which is a result from a translocation between chromosomes 9 and 22 in the hematopoietic stem cell. As an outcome, a Philadelphia (Ph) chromosome is formed. BCR-ABL causes disturbed cell proliferation among other things. Although targeted tyrosine kinase inhibitor therapy has been developed in the beginning of the millenium and the survival rate has increased significantly, it is still not known why some patients benefit more from the treatment than others. Furthermore, the therapy is not considered to be curative. Before the era of tyrosine kinase inhibitors, the first-line treatment for CML was interferon-? (IFN-?). However, only a small proportion of patients benefitted from the treatment. Of these patients, a few were able to discontinue the treatment without renewal of the disease. The mechanism of IFN-? is not completely understood, but it is believed that differences in the immune system can be one of the reasons why some patients have better therapy response. Kreutzman, Rohon et al. have recently discovered that patients who have been able to stop IFN-? treatment have an increased number of NK- and T-cells. They also have a unique clonal T-cell population and more cytotoxic CD8+ T-cells and less CD4+ T-cells. The aim of this masterâs thesis was to study the function of T- and NK-cells in IFN-? treated patients. Although it was shown earlier that IFN-? treated patients have increased NK-cell count, the function of these cells was unknown. Therefore, we have now investigated the killing potential of patientsâ NK-cells, their activation status and cell surface antigen expression. In addition, we have also studied the activation status of patientsâ T-cells and their cytotoxic properties. We observed that NK-cells from patients treated with IFN-? are unable to kill leukemic cells (K562) than NK-cells from healthy controls. In addition, patients on IFN-? treatment have more active T-cells and their NK-cells have an undifferentiated immunoregulatory phenotype. Patients that have been able to stop the treatment have anergic T-and NK-cells. As a conclusion our results suggest that IFN-? therapy induces increased NK-cell count, NK-cell immunoregulatory functions and more active T-cells. After stopping IFN-? therapy, NK- and T-cells from CML patients restore anergy typical for CML.

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Reactive oxygen species (ROS) have important functions in plant stress responses and development. In plants, ozone and pathogen infection induce an extracellular oxidative burst that is involved in the regulation of cell death. However, very little is known about how plants can perceive ROS and regulate the initiation and the containment of cell death. We have identified an Arabidopsis thaliana protein, GRIM REAPER (GRI), that is involved in the regulation of cell death induced by extracellular ROS. Plants with an insertion in GRI display an ozone-sensitive phenotype. GRI is an Arabidopsis ortholog of the tobacco flower-specific Stig1 gene. The GRI protein appears to be processed in leaves with a release of an N-terminal fragment of the protein. Infiltration of the N-terminal fragment of the GRI protein into leaves caused cell death in a superoxide-and salicylic acid-dependent manner. Analysis of the extracellular GRI protein yields information on how plants can initiate ROS-induced cell death during stress response and development.

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The role of FSH and diurnal testosterone rhythms in specific germ cell transformations during spermatogenesis were investigated using DNA flow cytometry and morphometry of the seminiferous epithelium of the adult male bonnet monkey (Macaca radiata), the endogenous hormone levels of which were altered by two different protocols. (1) Active immunization of five monkeys for 290 days using ovine FSH adsorbed on Alhydrogel resulted in the neutralization of endogenous FSH, leaving the LH and diurnal testosterone rhythms normal. (2) Desensitization of the pituitary gonadotrophs of ten monkeys by chronically infusing gonadotrophin-releasing hormone analogue, buserelin (50 micrograms/day release rate), via an Alzet pump implant (s.c.) led to a 60-80% reduction in LH and FSH as well as total abolition of testosterone rhythms. The basal testosterone level (3.3 +/- 2.0 micrograms/l), however, was maintained in this group by way of an s.c. testosterone silicone elastomer implant. Both of the treatments caused significant (P < 0.01) nearly identical reduction in testicular biopsy scores, mitotic indices and daily sperm production rates compared with respective controls. The germ cell DNA flow cytometric profiles of the two treatment groups, however, were fundamentally different from each other. The pituitary-desensitized group exhibited a significant (P < 0.001) increase in 2C (spermatogonial) and decrease in 1C (round spermatid) populations while S-phase (preleptotene spermatocytes) and 4C (primary spermatocytes) populations were normal, indicating an arrest in meiosis caused presumably by the lack of increment in nocturnal serum testosterone. In contrast, in the FSH-immunized group, at day 80 when the FSH deprivation was total, the primary block appeared to be at the conversion of spermatogonia (2C) to cells in S-phase and primary spermatocytes (4C reduced by > 90%). In addition, at this time, although the round spermatid (1C) population was reduced by 65% (P < 0.01) the elongate spermatid (HC) population showed an increase of 52% (P < 0.05). This, taken together with the fact that sperm output in the ejaculate is reduced by 80%, suggests a blockade in spermiogenesis and spermiation. Administration of booster injections of oFSH at time-points at which the antibody titre was markedly low (at days 84 and 180) resulted in a transient resurgence in spermatogenesis (at day 180 and 228), and this again was blocked by day 290 when the FSH antibody titre increased.

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Moonlighting functions have been described for several proteins previously thought to localize exclusively in the cytoplasm of bacterial or eukaryotic cells. Moonlighting proteins usually perform conserved functions, e. g. in glycolysis or as chaperonins, and their traditional and moonlighting function(s) usually localize to different cell compartments. The most characterized moonlighting proteins in Grampositive bacteria are the glycolytic enzymes enolase and glyceraldehyde-3-phosphate dehydrogenase (GAPDH), which function in bacteria-host interactions, e. g. as adhesins or plasminogen receptors. Research on bacterial moonlighting proteins has focused on Gram-positive bacterial pathogens, where many of their functions have been associated with bacterial virulence. In this thesis work I show that also species of the genus Lactobacillus have moonlighting proteins that carry out functions earlier associated with bacterial virulence only. I identified enolase, GAPDH, glutamine synthetase (GS), and glucose-6-phosphate isomerase (GPI) as moonlighting proteins of Lactobacillus crispatus strain ST1 and demonstrated that they are associated with cell surface and easily released from the cell surface into incubation buffer. I also showed that these lactobacillar proteins moonlight either as adhesins with affinity for basement membrane and extracellular matrix proteins or as plasminogen receptors. The mechanisms of surface translocation and anchoring of bacterial moonlighting proteins have remained enigmatic. In this work, the surface localization of enolase, GAPDH, GS and GPI was shown to depend on environmental factors. The members of the genus Lactobacillus are fermentative organisms that lower the ambient pH by producing lactic acid. At acidic pH enolase, GAPDH, GS and GPI were associated with the cell surface, whereas at neutral pH they were released into the buffer. The release did not involve de novo protein synthesis. I showed that purified recombinant His6-enolase, His6-GAPDH, His6-GS and His6-GPI reassociate with cell wall and bind in vitro to lipoteichoic acids at acidic pH. The in-vitro binding of these proteins localizes to cell division septa and cell poles. I also show that the release of moonlighting proteins is enhanced in the presence of cathelicidin LL- 37, which is an antimicrobial peptide and a central part of the innate immunity defence. I found that the LL-37-induced detachment of moonlighting proteins from cell surface is associated with cell wall permeabilization by LL-37. The results in this thesis work are compatible with the hypothesis that the moonlighting proteins of L. crispatus associate to the cell wall via electrostatic or ionic interactions and that they are released into surroundings in stress conditions. Their surface translocation is, at least in part, a result from their release from dead or permeabilized cells and subsequent reassociation onto the cell wall. The results of this thesis show that lactobacillar cells rapidly change their surface architecture in response to environmental factors and that these changes influence bacterial interactions with the host.