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1
Han, Doo-Hee, Min-Kyung Joe, Junsu Shin, Hong-Gye Sung, and Su-Kyum Kim. "Numerical Analysis on Plasma Particles inside Electro-magnetic Field Using Particle-in-cell Method." Journal of the Korean Society for Aeronautical & Space Sciences 45, no. 11 (2017): 932–38. http://dx.doi.org/10.5139/jksas.2017.45.11.932.
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Dentler, William. "Intraflagellar transport (IFT) during assembly and disassembly of Chlamydomonas flagella." Journal of Cell Biology 170, no. 4 (2005): 649–59. http://dx.doi.org/10.1083/jcb.200412021.
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Intraflagellar transport (IFT) of particles along flagellar microtubules is required for the assembly and maintenance of eukaryotic flagella and cilia. In Chlamydomonas, anterograde and retrograde particles viewed by light microscopy average 0.12-μm and 0.06-μm diameter, respectively. Examination of IFT particle structure in growing flagella by electron microscopy revealed similar size aggregates composed of small particles linked to each other and to the membrane and microtubules. To determine the relationship between the number of particles and flagellar length, the rate and frequency of IFT particle movement was measured in nongrowing, growing, and shortening flagella. In all flagella, anterograde and retrograde IFT averaged 1.9 μm/s and 2.7 μm/s, respectively, but retrograde IFT was significantly slower in flagella shorter than 4 μm. The number of flagellar IFT particles was not fixed, but depended on flagellar length. Pauses in IFT particle entry into flagella suggest the presence of a periodic “gate” that permits up to 4 particles/s to enter a flagellum.
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Bohrmann, J., and K. Biber. "Cytoskeleton-dependent transport of cytoplasmic particles in previtellogenic to mid-vitellogenic ovarian follicles of Drosophila: time-lapse analysis using video-enhanced contrast microscopy." Journal of Cell Science 107, no. 4 (1994): 849–58. http://dx.doi.org/10.1242/jcs.107.4.849.
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In Drosophila oogenesis, several morphogenetic determinants and other developmental factors synthesized in the nurse cells have been shown to accumulate in the oocyte during pre- to mid-vitellogenic stages. However, the mechanisms of the involved intercellular transport processes that seem to be rather selective have not been revealed so far. We have investigated in vitro, by means of video-enhanced contrast time-lapse microscopy, the transport of cytoplasmic particles from the nurse cells through ring canals into the oocyte during oogenesis stages 6–10A. At stage 7, we first observed single particles moving into the previtellogenic oocyte. The particle transfer was strictly unidirectional and seemed to be selective, since only some individual particles moved whereas other particles lying in the vicinity of the ring canals were not transported. The observed transport processes were inhibitable with 2,4-dinitrophenol, cytochalasin B or N-ethylmaleimide, but not with microtubule inhibitors. At the beginning of vitellogenesis (stage 8), the selective translocation of particles through the ring canals became faster (up to 130 nm/second) and more frequent (about 1 particle/minute), whereas during mid-vitellogenesis (stages 9–10A) the velocity and the frequency of particle transport decreased again. Following their more or less rectilinear passage through the ring canals, the particles joined a circular stream of cytoplasmic particles in the oocyte. This ooplasmic particle streaming started at stage 6/7 with velocities of about 80 nm/second and some reversals of direction at the beginning. The particle stream in the oocyte was sensitive to colchicine and vinblastine, but not to cytochalasin B, and we presume that it reflects the rearrangement of ooplasmic microtubules described recently by other authors. We propose that during stages 7–10A, a selective transport of particles into the oocyte occurs through the ring canal along a polarized scaffold of cytoskeletal elements in which microfilaments are involved. This transport might be driven by a myosin-like motor molecule. Either attached to, or organized into, such larger particles or organelles, specific mRNAs and proteins might become selectively transported into the oocyte.
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Ince, C., J. M. Coremans, D. L. Ypey, P. C. Leijh, A. A. Verveen, and R. van Furth. "Phagocytosis by human macrophages is accompanied by changes in ionic channel currents." Journal of Cell Biology 106, no. 6 (1988): 1873–78. http://dx.doi.org/10.1083/jcb.106.6.1873.
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The present study has shown that changes in ionic channel currents accompany the phagocytosis of particles by mononuclear phagocytes. The patch-clamp technique in the cell-attached configuration was applied to human monocyte-derived macrophages to measure the activity of single transmembrane ionic channels in intact cells. During such measurements, IgG-opsonized and non-opsonized latex particles were offered for phagocytosis under continuous video-microscopical observation. Single particles were presented to the phagocytes at a membrane location some distance from that of the patch electrode. After a lag period following particle attachment, enhanced inward and outward time-variant single channel currents coinciding with particle engulfment were observed. On the basis of current-voltage characteristics and membrane potential measurements, the outward-directed channels were identified as K+ channels. Phagocytosis was also accompanied by slow transient changes in background membrane currents, probably due to changes in the membrane potential of the phagocytosing cell. Phagocytosis of IgG-coated latex particles differed from phagocytosis of uncoated or albumin-coated particles by a shorter lag time between particle attachment and the onset of enhanced ionic channel activity.
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Kanaseki, T., Y. Ikeuchi, H. Sugiura, and T. Yamauchi. "Structural features of Ca2+/calmodulin-dependent protein kinase II revealed by electron microscopy." Journal of Cell Biology 115, no. 4 (1991): 1049–60. http://dx.doi.org/10.1083/jcb.115.4.1049.
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The molecular conformation of Ca2+/calmodulin-dependent protein kinase II (CaM kinase II) from the rat forebrain and cerebellum was studied by means of EM using a quick-freezing technique. Each molecule appeared to be composed of two kinds of particles, with one larger central particle and smaller peripheral particles and had shapes resembling that of a flower with 8 or 10 "petals". A favorable shadowing revealed that each peripheral particle had a thin link to the central particle. We predicted that the 8-petal molecules and 10-petal molecules were octamers and decamers of CaM kinase II subunits, respectively, each assembled with the association domains of subunits gathered in the center, and the catalytic domains in the peripheral particles. Binding of antibodies to the enzyme molecules suggested that molecules with 8 and 10 peripheral particles were homopolymers composed only of beta subunit and of alpha subunit, respectively, specifying that CaM kinase II consists of homopolymer of either alpha or beta subunits.
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Ingenito, Francesco, Pierluigi Andreoli, Dimitri Batani, et al. "Directional Track Selection Technique in CR39 SSNTD for lowyield reaction experiments." EPJ Web of Conferences 167 (2018): 05006. http://dx.doi.org/10.1051/epjconf/201816705006.
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There is a great interest in the study of p-11B aneutronic nuclear fusion reactions, both for energy production and for determination of fusion cross-sections at low energies. In this context we performed experiments at CELIA in which energetic protons, accelerated by the laser ECLIPSE, were directed toward a solid Boron target. Because of the small cross-sections at these energies the number of expected reactions is low. CR39 Solid-State Nuclear Track Detectors (SSNTD) were used to detect the alpha particles produced. Because of the low expected yield, it is difficult to discriminate the tracks due to true fusion products from those due to natural background in the CR39. To this purpose we developed a methodology of particle recognition according to their direction with respect to the detector normal, able to determine the position of their source. We applied this to the specific experiment geometry, so to select from all the tracks those due to particles coming from the region of interaction between accelerated protons and solid boron target. This technique can be of great help on the analysis of SSNTD in experiments with low yield reactions, but can be also generally applied to any experiment where particles reach the track detector with known directions, and for example to improve the detection limit of particle spectrometers using CR39.
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Niisuke, Katrin, Zsuzsanna Kuklenyik, Katalin V. Horvath, Michael S. Gardner, Christopher A. Toth, and Bela F. Asztalos. "Composition-function analysis of HDL subpopulations: influence of lipid composition on particle functionality." Journal of Lipid Research 61, no. 3 (2020): 306–15. http://dx.doi.org/10.1194/jlr.ra119000258.
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The composition-function relationship of HDL particles and its effects on the mechanisms driving coronary heart disease (CHD) is poorly understood. We tested the hypothesis that the functionality of HDL particles is significantly influenced by their lipid composition. Using a novel 3D-separation method, we isolated five different-sized HDL subpopulations from CHD patients who had low preβ-1 functionality (low-F) (ABCA1-dependent cholesterol-efflux normalized for preβ-1 concentration) and controls who had either low-F or high preβ-1 functionality (high-F). Molecular numbers of apoA-I, apoA-II, and eight major lipid classes were determined in each subpopulation by LC-MS. The average number of lipid molecules decreased from 422 in the large spherical α-1 particles to 57 in the small discoid preβ-1 particles. With decreasing particle size, the relative concentration of free cholesterol (FC) decreased in α-mobility but not in preβ-1 particles. Preβ-1 particles contained more lipids than predicted; 30% of which were neutral lipids (cholesteryl ester and triglyceride), indicating that these particles were mainly remodeled from larger particles not newly synthesized. There were significant correlations between HDL-particle functionality and the concentrations of several lipids. Unexpectedly, the phospholipid:FC ratio was significantly correlated with large-HDL-particle functionality but not with preβ-1 functionality. There was significant positive correlation between particle functionality and total lipids in high-F controls, indicating that the lipid-binding capacity of apoA-I plays a major role in the cholesterol efflux capacity of HDL particles. Functionality and lipid composition of HDL particles are significantly correlated and probably both are influenced by the lipid-binding capacity of apoA-I.
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Bovia, F., and K. Strub. "The signal recognition particle and related small cytoplasmic ribonucleoprotein particles." Journal of Cell Science 109, no. 11 (1996): 2601–8. http://dx.doi.org/10.1242/jcs.109.11.2601.
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Recently, a number of novel small cytoplasmic ribonucleoprotein particles have been identified that comprise RNA and protein subunits related to the signal recognition particle (SRP). Here we discuss the latest results on the structure and functions of SRP together with the structures and putative functions of the novel SRP-related ribonucleoprotein particles.
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Wada, Yuuko, Toshikazu Hamasaki, and Peter Satir. "Evidence for a Novel Affinity Mechanism of Motor-assisted Transport Along Microtubules." Molecular Biology of the Cell 11, no. 1 (2000): 161–69. http://dx.doi.org/10.1091/mbc.11.1.161.
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In microtubule (MT) translocation assays, using colloidal gold particles coupled to monoclonal tubulin antibodies to mark positions along MTs, we found that relative motion is possible between the gold particle and an MT, gliding on dynein or kinesin. Such motion evidently occurred by an affinity release and rebinding mechanism that did not require motor activity on the particle. As the MTs moved, particles drifted to the trailing edge of the MT and then were released. Sometimes the particles transferred from one MT to another, moving orthogonally. Although motion of the particles was uniformly rearward, movement was toward the (−) or (+) end of the MT, depending on whether dynein or kinesin, respectively, was used in the assay. These results open possibilities for physiological mechanisms of organelle and other movement that, although dependent on motor-driven microtubule transport, do not require direct motor attachment between the organelle and the microtubule. Our observations on the direction of particle drift and time of release may also provide confirmation in a dynamic system for the conclusion that β tubulin is exposed at the (+) end of the MT.
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Morrissette, N. S., J. M. Murray, and D. S. Roos. "Subpellicular microtubules associate with an intramembranous particle lattice in the protozoan parasite Toxoplasma gondii." Journal of Cell Science 110, no. 1 (1997): 35–42. http://dx.doi.org/10.1242/jcs.110.1.35.
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Application of Fourier analysis techniques to images of isolated, frozen-hydrated subpellicular microtubules from the protozoan parasite Toxoplasma gondii demonstrates a distinctive 32 nm periodicity along the length of the microtubules. A 32 nm longitudinal repeat is also observed in the double rows of intramembranous particles seen in freeze-fracture images of the parasite's pellicle; these rows are thought to overlie the subpellicular microtubules. Remarkably, the 32 nm intramembranous particle periodicity is carried over laterally to the single rows of particles that lie between the microtubule-associated double rows. This creates a two-dimensional particle lattice, with the second dimension at an angle of approximately 75 degrees to the longitudinal rows (depending on position along the length of the parasite). Drugs that disrupt known cytoskeletal components fail to destroy the integrity of the particle lattice. This intramembranous particle organization suggests the existence of multiple cytoskeletal filaments of unknown identity. Filaments associated with the particle lattice provide a possible mechanism for motility and shape change in Toxoplasma: distortion of the lattice may mediate the twirling motility seen upon host-cell lysis, and morphological changes observed during invasion.
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Veras, P. S., C. de Chastellier, M. F. Moreau, et al. "Fusion between large phagocytic vesicles: targeting of yeast and other particulates to phagolysosomes that shelter the bacterium Coxiella burnetii or the protozoan Leishmania amazonensis in Chinese hamster ovary cells." Journal of Cell Science 107, no. 11 (1994): 3065–76. http://dx.doi.org/10.1242/jcs.107.11.3065.
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This report examines the fusion of phagocytic vesicles with the large phagolysosome-like vacuoles induced in Chinese hamster ovary cells by the bacterium Coxiella burnetti or the Protozoan flagellate Leishmania amazonensis. Infection by these organisms is compatible with cell survival and multiplication. Fusion was inferred from the transfer of microscopically identifiable particles from donor to target vesicles. Donor vesicles contained heat-killed yeast, zymosan, beta-glucan or latex beads taken up by the host cells. Yeast and zymosan were also coated with Concanavalin A to increase their uptake by the cells (Goldman, R., Exp. Cell Res. 104, 325–334, 1977). Particle localization, routinely ascertained by phase-contrast microscopy, was confirmed by confocal laser fluorescence and by transmission electron microscopy. Coxiella vacuoles admitted all the particles tested and transfer took place whether the particles were given to the cells prior to or after infection. Transfer of uncoated or Concanavalin-A-coated yeast or zymosan was dependent on the number of particles ingested and on the incubation period (between 2 and 24 hours). Furthermore, the transfer step was quite efficient, since over 85% of the particles ingested entered Coxiella vacuoles at all particle to cell ratios examined. The fraction of uncoated or Concanavalin-A-coated yeast or zymosan transferred to Leishmania vacuoles was consistently lower and diminished at higher particle loads. In addition, only rarely did latex beads enter these vacuoles. The models proposed may be useful for the delineation of biochemical and molecular mechanisms involved in the fusion of large phagocytic vesicles and the modulation of the latter by cellular and pathogen-derived signals.
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Glickman, Michael H., David M. Rubin, Victor A. Fried, and Daniel Finley. "The Regulatory Particle of the Saccharomyces cerevisiae Proteasome." Molecular and Cellular Biology 18, no. 6 (1998): 3149–62. http://dx.doi.org/10.1128/mcb.18.6.3149.
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ABSTRACT The proteasome is a multisubunit protease responsible for degrading proteins conjugated to ubiquitin. The 670-kDa core particle of the proteasome contains the proteolytic active sites, which face an interior chamber within the particle and are thus protected from the cytoplasm. The entry of substrates into this chamber is thought to be governed by the regulatory particle of the proteasome, which covers the presumed channels leading into the interior of the core particle. We have resolved native yeast proteasomes into two electrophoretic variants and have shown that these represent core particles capped with one or two regulatory particles. To determine the subunit composition of the regulatory particle, yeast proteasomes were purified and analyzed by gradient sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Resolution of the individual polypeptides revealed 17 distinct proteins, whose identities were determined by amino acid sequence analysis. Six of the subunits have sequence features of ATPases (Rpt1 to Rpt6). Affinity chromatography was used to purify regulatory particles from various strains, each of which expressed one of the ATPases tagged with hexahistidine. In all cases, multiple untagged ATPases copurified, indicating that the ATPases assembled together into a heteromeric complex. Of the remaining 11 subunits that we have identified (Rpn1 to Rpn3 and Rpn5 to Rpn12), 8 are encoded by previously described genes and 3 are encoded by genes not previously characterized for yeasts. One of the previously unidentified subunits exhibits limited sequence similarity with deubiquitinating enzymes. Overall, regulatory particles from yeasts and mammals are remarkably similar, suggesting that the specific mechanistic features of the proteasome have been closely conserved over the course of evolution.
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Iomini, Carlo, Veronica Babaev-Khaimov, Massimo Sassaroli, and Gianni Piperno. "Protein Particles in Chlamydomonas Flagella Undergo a Transport Cycle Consisting of Four Phases." Journal of Cell Biology 153, no. 1 (2001): 13–24. http://dx.doi.org/10.1083/jcb.153.1.13.
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We used an improved procedure to analyze the intraflagellar transport (IFT) of protein particles in Chlamydomonas and found that the frequency of the particles, not only the velocity, changes at each end of the flagella. Thus, particles undergo structural remodeling at both flagellar locations. Therefore, we propose that the IFT consists of a cycle composed of at least four phases: phases II and IV, in which particles undergo anterograde and retrograde transport, respectively, and phases I and III, in which particles are remodeled/exchanged at the proximal and distal end of the flagellum, respectively. In support of our model, we also identified 13 distinct mutants of flagellar assembly (fla), each defective in one or two consecutive phases of the IFT cycle. The phase I-II mutant fla10-1 revealed that cytoplasmic dynein requires the function of kinesin II to participate in the cycle. Phase I and II mutants accumulate complex A, a particle component, near the basal bodies. In contrast, phase III and IV mutants accumulate complex B, a second particle component, in flagellar bulges. Thus, fla mutations affect the function of each complex at different phases of the cycle.
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Sundaresan, Vignesh, Joseph W. Monaghan, and Katherine A. Willets. "Monitoring Simultaneous Electrochemical Reactions with Single Particle Imaging." ChemElectroChem 5, no. 20 (2018): 3052–58. http://dx.doi.org/10.1002/celc.201800715.
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Márquez, Augusto, Manuel J. Rodríguez-Pérez, Juan A. Anta, et al. "Defects in Porous Networks of WO3 Particle Aggregates." ChemElectroChem 3, no. 4 (2016): 658–67. http://dx.doi.org/10.1002/celc.201500435.
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Zaner, K. S., and P. A. Valberg. "Viscoelasticity of F-actin measured with magnetic microparticles." Journal of Cell Biology 109, no. 5 (1989): 2233–43. http://dx.doi.org/10.1083/jcb.109.5.2233.
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Dispersed submicroscopic magnetic particles were used to probe viscoelasticity for cytoplasm and purified components of cytoplasm. An externally applied magnetic field exerted force on particles in cells, in filamentous actin (F-actin) solutions, or in F-actin gels formed by the addition of the actin gelation factor, actin-binding protein (ABP). The particle response to magnetic torque can be related to the viscoelastic properties of the fluids. We compared data obtained on F-actin by the magnetic particle method with data obtained on F-actin by means of a sliding plane viscoelastometer. F-actin solutions had a significant elasticity, which increased by 20-fold when gels were formed by ABP addition. Both methods gave consistent results, but the dispersed magnetic particles indicated quantitatively greater rigidity than the viscoelastometer (two and six times greater for F-actin solutions and for F-actin plus ABP gels, respectively). These differences may be due to the fact that, compared with traditional microrheometers, dispersed particle measurements are less affected by long-range heterogeneity or domain-like structure. The magnetometric method was used to examine the mechanical properties of cytoplasm within intact macrophages; the application of the same magnetometric technique to both cells and well-defined, purified protein systems is a first step toward interpreting the results obtained for living cells in molecular terms. The magnetic particle probe system is an effective nonoptical technique for determining the motile and mechanical properties of cells in vitro and in vivo.
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Savulescu, Anca F., Hagai Shorer, Oded Kleifeld, et al. "Nuclear import of an intact preassembled proteasome particle." Molecular Biology of the Cell 22, no. 6 (2011): 880–91. http://dx.doi.org/10.1091/mbc.e10-07-0595.
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The 26S proteasome is a conserved 2.5 MDa protein degradation machine that localizes to different cellular compartments, including the nucleus. Little is known about the specific targeting mechanisms of proteasomes in eukaryotic cells. We used a cell-free nuclear reconstitution system to test for nuclear targeting and import of distinct proteasome species. Three types of stable, proteolytically active proteasomes particles were purified from Xenopus egg cytosol. Two of these, the 26S holoenzyme and the 20S core particle, were targeted to the nuclear periphery but did not reach the nucleoplasm. This targeting depends on the presence of mature nuclear pore complexes (NPCs) in the nuclear envelope. A third, novel form, designated here as 20S+, was actively imported through NPCs. The 20S+ proteasome particle resembles recently described structural intermediates from other systems. Nuclear import of this particle requires functional NPCs, but it is not directly regulated by the Ran GTPase cycle. The mere presence of the associated “+” factors is sufficient to reconstitute nuclear targeting and confer onto isolated 20S core particles the ability to be imported. Stable 20S+ particles found in unfertilized eggs may provide a means for quick mobilization of existing proteasome particles into newly formed nuclear compartments during early development.
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Kozako, Tomohiro, Katsuhiko Fukada, Shinya Hirata, et al. "Efficient Induction of HTLV-1-Specific CTL Response by HTLV-1/HBc Chimeric Particle without Adjuvant as a Prophylactic for HTLV-1- Associated T-Cell Leukemia." Blood 112, no. 11 (2008): 84. http://dx.doi.org/10.1182/blood.v112.11.84.84.
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Abstract Adult T-cell leukemia/lymphoma (ATLL) is an aggressive peripheral T-cell neoplasm that develops only after long-term chronic infection with human T-cell leukemia virus-1 (HTLV-1). HTLV-1-specific Cytotoxic T lymphocytes (CTL) play an important role in suppressing proliferation of HTLV-1-infected or transformed T cells in vitro. The development of ATLL in approximately 2% of persons chronically infected with HTLV-1 may suggest a specific immunegenetic background predisposing to CTL failure in a proportion of HTLV-1 carriers. On the other hand, virus like particle is demonstrated to induce stronger humoral, T helper and cytotoxic T-cell responses without adjuvant. As free synthetic peptides or proteins are usually poor immunogens, the hepatitis B core (HBc) particle is a potential target carrier protein to induce immunity without use of an adjuvant. In this study, we examined the efficient induction of HTLV-1-specific CD8+ T-cell response by HTLV-1/HBc chimeric particles inserting HLA-A*0201-restricted HTLV-1 Tax-epitope without adjuvant (Figure 1). The immunization of HLA-A*0201 transgenic mice with the chimeric particle induced antigen-specific IFN-□ reaction by ELISPOT assay, whereas epitope peptide only induced no reaction (Figure 2). HTLV-1/HLA tetramer assay detected induction of HTLV-1-specific CD8+ T-cells in both splenic and inguinal lymph node cells by HTLV-1/HBc chimera particles. Furthermore, upon exposure of these dendritic cells (DCs) to the chimeric particles, the expression of CD86 was increased in a dose-dependent manner. These results suggest that HTLV-1/HBc chimeric particles are capable of inducing strong cellular immune responses without adjuvant via effective maturation of DCs and are potentially useful as an effective vaccine carrier for the treatment of cancers and infectious diseases by varying the epitope peptide. Figure 1. Electronmicrographs of recombinant HTLV-1 Tax/HBc chimeric particles. Figure 1. Electronmicrographs of recombinant HTLV-1 Tax/HBc chimeric particles. Figure 2. Induction of cellular immunity by intradermal immunization with HTLV-1/HBc chimeric particle. Mice were immunized twice with recombinant HTLV-1/HBc chimeric particle, HTLV-1 peptide and HTLV-1 peptide + HBc particle. The number of IFN-□-producing cells was measured by ELISPOT assay. IFN-□ spots show the number of peptide-loaded target cells to peptide-unloaded target cells. *P<0.05, **P<0.01 vs PBS group. The experiments were performed in triplicate. Mean S.E. are shown in the results. Figure 2. Induction of cellular immunity by intradermal immunization with HTLV-1/HBc chimeric particle. Mice were immunized twice with recombinant HTLV-1/HBc chimeric particle, HTLV-1 peptide and HTLV-1 peptide + HBc particle. The number of IFN-□-producing cells was measured by ELISPOT assay. IFN-□ spots show the number of peptide-loaded target cells to peptide-unloaded target cells. *P<0.05, **P<0.01 vs PBS group. The experiments were performed in triplicate. Mean S.E. are shown in the results.
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Kucik, D. F., S. C. Kuo, E. L. Elson, and M. P. Sheetz. "Preferential attachment of membrane glycoproteins to the cytoskeleton at the leading edge of lamella." Journal of Cell Biology 114, no. 5 (1991): 1029–36. http://dx.doi.org/10.1083/jcb.114.5.1029.
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The active forward movement of cells is often associated with the rearward transport of particles over the surfaces of their lamellae. Unlike the rest of the lamella, we found that the leading edge (within 0.5 microns of the cell boundary) is specialized for rearward transport of membrane-bound particles, such as Con A-coated latex microspheres. Using a single-beam optical gradient trap (optical tweezers) to apply restraining forces to particles, we can capture, move and release particles at will. When first bound on the central lamellar surface, Con A-coated particles would diffuse randomly; when such bound particles were brought to the leading edge of the lamella with the optical tweezers, they were often transported rearward. As in our previous studies, particle transport occurred with a concurrent decrease in apparent diffusion coefficient, consistent with attachment to the cytoskeleton. For particles at the leading edge of the lamella, weak attachment to the cytoskeleton and transport occurred with a half-time of 3 s; equivalent particles elsewhere on the lamella showed no detectable attachment when monitored for several minutes. Particles held on the cell surface by the laser trap attached more strongly to the cytoskeleton with time. These particles could escape a trapping force of 0.7 X 10(-6) dyne after 18 +/- 14 (sd) s at the leading edge, and after 64 +/- 34 (SD) s elsewhere on the lamella. Fluorescent succinylated Con A staining showed no corresponding concentration of general glycoproteins at the leading edge, but cytochalasin D-resistant filamentous actin was found at the leading edge. Our results have implications for cell motility: if the forces used for rearward particle transport were applied to a rigid substratum, cells would move forward. Such a mechanism would be most efficient if the leading edge of the cell contained preferential sites for attachment and transport.
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Pan, Yung-Wei, and Peter Kurre. "Evidence for Cellular Uptake and Subsequent Release of HIV-Derived Vector Particles after Ex Vivo Transduction Culture of Hematopoietic Cells." Blood 108, no. 11 (2006): 3250. http://dx.doi.org/10.1182/blood.v108.11.3250.3250.
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Abstract Retroviral vectors based on Human Immunodeficiency Virus (HIV) and pseudotyped with vesicular stomatitis virus G (VSV-G) envelope glycoprotein can stably modify non-dividing hematopoietic stem cells. Ex vivo culture of vector particles and target cells is presumed to result in receptor mediated particle uptake by the cell and successful proviral integration, or degradation. However, recent evidence in dendritic cells suggests an alternate cellular fate for vector particles whereby they persist in exosomes and can be released to transduce secondary targets. We investigated the existence and consequences of such a pathway in other hematopoietic target cells after conventional ex vivo exposure. Murine bone marrow cells (5×10^5) were exposed to vector particles (2.5 ×10^6), washed twice, and placed alongside 293T fibroblasts (1×10^5). Direct, or transwell, co-culture resulted in GFP marking of 30% and 10% of secondary targets (ie. 293T cells), respectively. Transgene expression in 293T cells was stable over time in culture, abrogated by using integration-deficient particles, and reflected proviral integration, based on real-time PCR results. Cellular persistence of particles after primary exposure of murine whole bone marrow or SupT1 cells and secondary carryover were vector concentration dependent and pseudotype independent. Intriguingly, cell bound vector particles were selectively protected from serum inactivation, and the kinetics of secondary transduction suggested a prolonged particle half-life, when compared to particles cultured under cell-free conditions. Further, while direct protease exposure effectively eliminated vector infectivity, secondary transfer of particles from vector exposed, protease washed, cells was only partially inhibited, suggesting the uptake of particles in protease-inaccessible compartments of primary targets. When comparing vector exposures at 37 C versus 4 C (preventing particle uptake while permitting binding), again followed by protease treatment, secondary gene transfer was relatively greater at 37 C and increased with primary transduction duration, consistent with progressive intracellular particle retention. Indeed, deconvolution microscopy experiments to investigate the fate of tagged particles after brief vector exposure to target cells revealed intracellular persistence and perinuclear accumulation. To determine the relevance of these in vitro findings, we next performed studies in non-ablated murine recipients (n=30) that received ex vivo vector exposed, and washed, whole bone marrow or lineage depleted cells. To unambiguously demonstrate particle hand-off to recipient hematopoietic cells, we used CD45.1 donors and CD45.2 recipient animals. Results demonstrated long-term GFP marking by flow-cytometry (up to 9%) and by real-time PCR in recipient bone marrow and peripheral blood leukocytes. Additional immuno stains at sacrifice showed GFP-marked -CD45 negative- cells in liver and spleen tissue sections. Gain of replication competency in vector lots and in serum from recipient animals was excluded by p24 ELISA assay. Based on these results we propose an alternate fate for VSV-G lentivector particles, involving cellular retention after ex vivo exposure to primary hematopoietic target cells, subsequent release, and secondary transduction of susceptible target tissues. These findings may have implications for a range of applications using lentiviral vectors.
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Cole, Douglas G., Dennis R. Diener, Amy L. Himelblau, Peter L. Beech, Jason C. Fuster, and Joel L. Rosenbaum. "Chlamydomonas Kinesin-II–dependent Intraflagellar Transport (IFT): IFT Particles Contain Proteins Required for Ciliary Assembly in Caenorhabditis elegans Sensory Neurons." Journal of Cell Biology 141, no. 4 (1998): 993–1008. http://dx.doi.org/10.1083/jcb.141.4.993.
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We previously described a kinesin-dependent movement of particles in the flagella of Chlamydomonas reinhardtii called intraflagellar transport (IFT) (Kozminski, K.G., K.A. Johnson, P. Forscher, and J.L. Rosenbaum. 1993. Proc. Natl. Acad. Sci. USA. 90:5519–5523). When IFT is inhibited by inactivation of a kinesin, FLA10, in the temperature-sensitive mutant, fla10, existing flagella resorb and new flagella cannot be assembled. We report here that: (a) the IFT-associated FLA10 protein is a subunit of a heterotrimeric kinesin; (b) IFT particles are composed of 15 polypeptides comprising two large complexes; (c) the FLA10 kinesin-II and IFT particle polypeptides, in addition to being found in flagella, are highly concentrated around the flagellar basal bodies; and, (d) mutations affecting homologs of two of the IFT particle polypeptides in Caenorhabditis elegans result in defects in the sensory cilia located on the dendritic processes of sensory neurons. In the accompanying report by Pazour, G.J., C.G. Wilkerson, and G.B. Witman (1998. J. Cell Biol. 141:979–992), a Chlamydomonas mutant (fla14) is described in which only the retrograde transport of IFT particles is disrupted, resulting in assembly-defective flagella filled with an excess of IFT particles. This microtubule- dependent transport process, IFT, defined by mutants in both the anterograde (fla10) and retrograde (fla14) transport of isolable particles, is probably essential for the maintenance and assembly of all eukaryotic motile flagella and nonmotile sensory cilia.
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D'Andrea, L., M. A. Danon, G. P. Sgourdas, and E. M. Bonder. "Identification of coelomocyte unconventional myosin and its association with in vivo particle/vesicle motility." Journal of Cell Science 107, no. 8 (1994): 2081–94. http://dx.doi.org/10.1242/jcs.107.8.2081.
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Sea urchin coelomocytes undergo an inducible structural transformation from petalloid to filopodial form during the ‘clotting’ response in sea urchins. Using a petalloid coelomocyte model, stimulated coelomocytes exhibited bidirectional particle/vesicle motility with a broad distribution of velocities, ranging from 0.02 to 0.12 microns s-1 in the outward bound direction. Coelomocytes treated with the microtubule-disrupting drug, nocodazole, continued to exhibit outward particle/vesicle movements along linear paths with an average velocity of 0.028 +/- 0.006 microns s-1. We partially purified a 110 kDa polypeptide possessing K+EDTA-, Ca2(+)-, Mg2(+)- and F-actin-activated Mg(2+)-ATPase activities characteristic of myosin-like motor proteins. The 110 kDa protein immuno-crossreacted with both affinity-purified, anti-brush border unconventional myosin-I polyclonal antibodies and anti-Acanthamoeba myosin head monoclonal antibodies. By indirect immunofluorescence, the 110 kDa unconventional myosin was localized to clusters of particles/vesicles within the perinuclear region of unstimulated coelomocytes, an area containing numerous mitochondria, acidic, lysosomal and Golgi organelles. Indirect immunofluorescence of partially transformed and filopodial coelomocytes detected a diminution of perinuclear staining with a concomitant appearance of stained linear arrays of particles/vesicles, enhanced staining of peripheral lamellae, and staining of the entire length of the filopodia. Subfractionation of unstimulated coelomocyte homogenates on linear sucrose gradients identified distinct peaks of ATPase activity associated with fractions containing conventional and 110 kDa unconventional myosin. Unconventional myosin-containing fractions were found to have numerous particles that stained with anti-brush border unconventional myosin-I antibodies and the lipophilic dye, DiOC6. Thus, coelomocytes demonstrate activatable movements of particles/vesicles in cells devoid of microtubules and possess an unconventional myosin, which may be the motor protein driving particle/vesicle translocation.
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Kendall, Michaela, Teresa D. Tetley, Edward Wigzell, Bernie Hutton, Mark Nieuwenhuijsen, and Paul Luckham. "Lung lining liquid modifies PM2.5 in favor of particle aggregation: a protective mechanism." American Journal of Physiology-Lung Cellular and Molecular Physiology 282, no. 1 (2002): L109—L114. http://dx.doi.org/10.1152/ajplung.2002.282.1.l109.
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The health effects of particle inhalation including urban air pollution and tobacco smoke comprise a significant public health concern worldwide, although the mechanisms by which inhaled particles cause premature deaths remain undetermined. In this study, we assessed the physicochemical interactions of fine airborne particles (PM2.5) and lung lining liquid using scanning electron microscopy, atomic force microscopy, and X-ray photon spectroscopy. We provide experimental evidence to show that lung lining liquid modifies the chemistry and attractive forces at the surface of PM2.5, which leads to enhanced particle aggregation. We propose that this is an important protective mechanism that aids particle clearance in the lung.
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Conway, G., J. Wooley, T. Bibring, and W. M. LeStourgeon. "Ribonucleoproteins package 700 nucleotides of pre-mRNA into a repeating array of regular particles." Molecular and Cellular Biology 8, no. 7 (1988): 2884–95. http://dx.doi.org/10.1128/mcb.8.7.2884-2895.1988.
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An assay for the in vitro assembly of HeLa cell 40S nuclear ribonucleoprotein particles (hnRNP particles) has been developed. The substrates were single-stranded nucleic acid polymers of defined length and sequence prepared in vitro and the six major core particle proteins from isolated 40S hnRNP. The fidelity of in vitro assembly was evaluated on various physical parameters, including sedimentation, salt dissociation, polypeptide stoichiometry, UV-activated protein-RNA cross-linking, and overall morphology. Correct particle assembly depended on RNA length and on the input protein/RNA ratio but not on the concentration of the reactant mixture nor on the presence or absence of internal RNA processing signals, a 5'-cap structure, a 3'-poly(A) moiety, or ATP as energy source. RNA lengths between 685 and 726 nucleotides supported correct particle assembly. Dimers and oligomeric complexes that possessed the same polypeptide stoichiometry as native hnRNP assembled on RNA chains that were integral multiples of 700 nucleotides. Intermediate-length RNA supported the assembly of nonstoichiometric complexes lacking structural homogeneity. An analysis of these complexes indicates that proteins A1 and A2 may be the first proteins to bind RNA during particle assembly. We conclude that the major proteins of 40S hnRNP particles contain the necessary information for packaging nascent transcripts into a repeating "ribonucleosomal" structure possessing a defined RNA length and protein composition but do not themselves contain the information for modulating packaging that may be required for RNA splicing.
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Greenberg, S., J. el Khoury, F. di Virgilio, E. M. Kaplan, and S. C. Silverstein. "Ca(2+)-independent F-actin assembly and disassembly during Fc receptor-mediated phagocytosis in mouse macrophages." Journal of Cell Biology 113, no. 4 (1991): 757–67. http://dx.doi.org/10.1083/jcb.113.4.757.
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Phagocytosis of IgG-coated particles by macrophages is presumed to involve the actin-based cytoskeleton since F-actin accumulates beneath forming phagosomes, and particle engulfment is blocked by cytochalasins, drugs that inhibit actin filament assembly. However, it is unknown whether Fc receptor ligation affects the rate or extent of F-actin assembly during phagocytosis of IgG-coated particles. To examine this question we have used a quantitative spectrofluorometric method to examine F-actin dynamics during a synchronous wave of phagocytosis of IgG-coated red blood cells by inflammatory mouse macrophages. We observed a biphasic rise in macrophage F-actin content during particle engulfment, with maxima at 1 and 5 min after the initiation of phagocytosis. F-actin declined to resting levels by 30 min, by which time particle engulfment was completed. These quantitative increases in macrophage F-actin were reflected in localized changes in F-actin distribution. Previous work showed that the number of IgG-coated particles engulfed by macrophages is unaffected by buffering extracellular calcium or by clamping cytosolic free calcium concentration ([Ca2+]i) to very low levels (Di Virgilio, F., B. C. Meyer, S. Greenberg, and S. C. Silverstein. 1988. J. Cell Biol. 106: 657-666). To determine whether clamping [Ca2+]i in macrophages affects the rate of particle engulfment, or the assembly or disassembly of F-actin during phagocytosis, we examined these parameters in macrophages whose [Ca2+]i had been clamped to approximately less than 3 nM with fura 2/AM and acetoxymethyl ester of EGTA. We found that the initial rate of phagocytosis, and the quantities of F-actin assembled and disassembled were similar in Ca(2+)-replete and Ca(2+)-depleted macrophages. We conclude that Fc receptor-mediated phagocytosis in mouse macrophages is accompanied by an ordered sequence of assembly and disassembly of F-actin that is insensitive to [Ca2+]i.
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Bellmann, Cornelia, Anja Caspari, and Karina Grundke. "Controlling of Surface Parameters of Particles Used for Electrocodeposition." Key Engineering Materials 412 (June 2009): 273–78. http://dx.doi.org/10.4028/www.scientific.net/kem.412.273.
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It is well known that colloid-chemical aspects, such as agglomeration processes, wetting and adsorption phenomena, have a decisive influence on the separation behaviour and coating quality of a composite plating. The following processing steps for electrocodeposition have to be considered: preparation of a stable dispersion of the particles in the electrolytic bath, transportation of the particles to the metal surface, adhesion of the particles onto the surface, incorporation of the particles in the metal matrix. Celis [1,2] and Hyashi [3] could show that ion adsorption onto the particle surface is very important for electrophoretic mobility and layer quality. On the other site, Fransaer and others [2,4] showed that surface free energy plays an important role for incorporation of particles in a metal matrix. They could demonstrate that hydrophilic particles do not make contact with the electrode, probably due to repulsive hydration forces. Hydrophobic particles make contact with the electrode, due to an attractive hydrophobic force. Hence it is important to have a method for estimating the hydrophilic/ hydrophobic surface properties of such particles to select a suitable surface modification strategy. A direct way to measure the surface free energy of solid particles is not available so far. Therefore, it is generally accepted to use the phenomenon of capillary penetration of liquids into porous media to determine the wetting properties of particles by measuring the penetration velocity of well-defined liquids in a powder packing. The kinetics of penetration correlates mainly to the geometric structure of the powder packing and the wettability of the particles. By using the equation-of-state approach for solid-liquid interfacial tensions the solid surface free energy of the particles can be determined [5]. In this paper, we show the usefulness of capillary penetration experiments and discuss some parameters that should be considered for the interpretation of the data. Ion adsorption processes, on the other hand, can be described by electrokinetic measurements [6,7].
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Kucik, D. F., E. L. Elson, and M. P. Sheetz. "Cell migration does not produce membrane flow." Journal of Cell Biology 111, no. 4 (1990): 1617–22. http://dx.doi.org/10.1083/jcb.111.4.1617.
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We have previously reported that rearward migration of surface particles on slowly moving cells is not driven by membrane flow (Sheetz, M. P., S. Turney, H. Qian, and E. L. Elson. 1989. Nature (Lond.). 340:284-288) and recent photobleaching measurements have ruled out any rapid rearward lipid flow (Lee, J., M. Gustafsson, D. E. Magnussen, and K. Jacobson. 1990. Science (Wash. DC.) 247:1229-1233). It was not possible, however, to conclude from those studies that a slower or tank-tread membrane lipid flow does not occur. Therefore, we have used the technology of single particle tracking to examine the movements of diffusing particles on rapidly locomoting fish keratocytes where the membrane current is likely to be greatest. The keratocytes had a smooth lamellipodial surface on which bound Con A-coated gold particles were observed either to track toward the nuclear region (velocity of 0.35 +/- 0.15 micron/s) or to diffuse randomly (apparent diffusion coefficient of [3.5 +/- 2.0] x 10(-10) cm2/s). We detected no systematic drift relative to the cell edge of particles undergoing random diffusion even after the cell had moved many micrometers. The average net particle displacement was 0.01 +/- 2.7% of the cell displacement. These results strongly suggest that neither the motions of membrane proteins driven by the cytoskeleton nor other possible factors produce a bulk flow of membrane lipid.
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Wessels, D., and D. R. Soll. "Myosin II heavy chain null mutant of Dictyostelium exhibits defective intracellular particle movement." Journal of Cell Biology 111, no. 3 (1990): 1137–48. http://dx.doi.org/10.1083/jcb.111.3.1137.
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Both cellular motility and intracellular particle movement are compared between normal Dictyostelium amebae of strain AX4 and amebae of a myosin II heavy chain null mutant, HS2215, using the computer assisted "Dynamic Morphology System." In AX4 cells rapidly translocating in buffer, cytoplasmic expansion is apical and the majority of intracellular particles move anteriorly, towards the site of expansion. When these cells are pulsed with 10(-6) M cAMP, the peak concentration of the natural cAMP wave, cells stop translocating and average particle velocity decreases threefold within 2-4 s after cAMP addition. After 8 s, there is a partial rebound both in cytoplasmic expansion and particle velocity, but in both cases, original apical polarity is lost. In HS2215 cells in buffer, both cellular translocation and average particle velocity are already at the depressed levels observed in normal cells immediately after cAMP addition, and no anterior bias is observed in either the direction of cytoplasmic expansion or the direction of particle movement. The addition of cAMP to myosin-minus cells results in no additional effect. The results demonstrate that myosin II is necessary for (a) the rapid rate of intracellular particle movement, (b) the biased anterior directionality of particle movement, and (c) the rapid inhibition of particle movement by cAMP.
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Bläubaum, Lars, Fridolin Röder, Christine Nowak, Hoon Seng Chan, Arno Kwade, and Ulrike Krewer. "Impact of Particle Size Distribution on Performance of Lithium‐Ion Batteries." ChemElectroChem 7, no. 23 (2020): 4755–66. http://dx.doi.org/10.1002/celc.202001249.
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Oh, Y. K., and J. A. Swanson. "Different fates of phagocytosed particles after delivery into macrophage lysosomes." Journal of Cell Biology 132, no. 4 (1996): 585–93. http://dx.doi.org/10.1083/jcb.132.4.585.
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Phagocytosis in macrophages is often studied using inert polymer microspheres. An implicit assumption in these studies is that such particles contain little or no specific information in their structure that affects their intracellular fate. We tested that assumption by examining macrophage phagosomes containing different kinds of particles and found that although all particles progressed directly to lysosomes, their subsequent fates varied. Within 15 min of phagocytosis, &gt;90% of phagosomes containing opsonized sheep erythrocytes, poly-e-caprolactone microspheres, polystyrene microspheres (PS), or polyethylene glycol-conjugated PS merged with the lysosomal compartment. After that point, however, the characteristics of phagolysosomes changed in several ways that indicated differing degrees of continued interaction with the lysosomal compartment. Sheep erythrocyte phagolysosomes merged together and degraded their contents quickly, poly-e-caprolactone phagolysosomes showed intermediate levels of interaction, and PS phagolysosomes became isolated within the cytoplasm. PS were relatively inaccessible to an endocytic tracer, Texas red dextran, added after phagocytosis. Moreover, immunofluorescent staining for the lysosomal protease cathepsin L decreased in PS phagolysosomes to 23% by 4 h after phagocytosis, indicating degradation of the enzyme without replacement. Finally, PS surface labeled with fluorescein-labeled albumin showed a markedly reduced rate of protein degradation in phagolysosomes, when compared to rates measured for proteins in or on other particles. Thus, particle chemistry affected both the degree of postlysosomal interactions with other organelles and, consequently, the intracellular half-life of particle-associated proteins. Such properties may affect the ability of particles to deliver macromolecules into the major histocompatibility complex class I and II antigen presentation pathways.
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Fang, Guibin, Yuan Fu, Shixun Li та ін. "The USP14–NLRC5 pathway inhibits titanium particle–induced osteolysis in mice by suppressing NF-κB and PI3K/AKT activities". Journal of Biological Chemistry 295, № 20 (2020): 7018–32. http://dx.doi.org/10.1074/jbc.ra119.012495.
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Total hip arthroplasty (THA) is a widely-used surgical intervention for treating patients with end-stage degenerative and inflammatory osteoarthropathy. However, wear particles from the artificial titanium joint can induce osteolysis, limiting the long-term survivorship of THA. Monocyte/macrophage lineage cells are the key players in the response to wear particles, and the proinflammatory NF-κB and phosphoinositide 3-kinase (PI3K)–AKT Ser/Thr kinase (AKT)-signaling pathways have been shown to be the most important contributors to wear particle–induced osteolysis. In contrast, ubiquitin-specific protease 14 (USP14) specifically removes the polyubiquitin chains from the nucleotide-binding and oligomerization domain (NOD)-like receptor family Caspase recruitment domain (CARD)–containing 5 (NLRC5) and thereby enhances the NLRC5-mediated inhibition of NF-κB signaling. In this study, we aimed to clarify the role of the USP14–NLRC5 pathway in wear particle–induced osteolysis in vitro and in vivo. We found that NLRC5 or USP14 overexpression inhibits titanium particle–induced proinflammatory tumor necrosis factor α (TNFα) production and NF-κB pathway activation, and it also decreases M1 macrophage polarization and PI3K/AKT pathway activation. Of note, NLRC5 and USP14 overexpression attenuated titanium particle–induced cranial osteolysis in mice. In conclusion, the findings of our study indicate that the USP14–NLRC5 pathway inhibits titanium particle–induced osteolysis by suppressing the NF-κB and PI3K/AKT pathways both in vitro and in vivo.
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Godsel, Lisa M., Sherry N. Hsieh, Evangeline V. Amargo, et al. "Desmoplakin assembly dynamics in four dimensions." Journal of Cell Biology 171, no. 6 (2005): 1045–59. http://dx.doi.org/10.1083/jcb.200510038.
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The intermediate filament (IF)–binding protein desmoplakin (DP) is essential for desmosome function and tissue integrity, but its role in junction assembly is poorly understood. Using time-lapse imaging, we show that cell–cell contact triggers three temporally overlapping phases of DP-GFP dynamics: (1) the de novo appearance of punctate fluorescence at new contact zones after as little as 3 min; (2) the coalescence of DP and the armadillo protein plakophilin 2 into discrete cytoplasmic particles after as little as 15 min; and (3) the cytochalasin-sensitive translocation of cytoplasmic particles to maturing borders, with kinetics ranging from 0.002 to 0.04 μm/s. DP mutants that abrogate or enhance association with IFs exhibit delayed incorporation into junctions, altering particle trajectory or increasing particle pause times, respectively. Our data are consistent with the idea that DP assembles into nascent junctions from both diffusible and particulate pools in a temporally overlapping series of events triggered by cell–cell contact and regulated by actin and DP–IF interactions.
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Esteban, R., and R. B. Wickner. "Three different M1 RNA-containing viruslike particle types in Saccharomyces cerevisiae: in vitro M1 double-stranded RNA synthesis." Molecular and Cellular Biology 6, no. 5 (1986): 1552–61. http://dx.doi.org/10.1128/mcb.6.5.1552-1561.1986.
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Killer strains of Saccharomyces cerevisiae bear at least two different double-stranded RNAs (dsRNAs) encapsidated in 39-nm viruslike particles (VLPs) of which the major coat protein is coded by the larger RNA (L-A dsRNA). The smaller dsRNA (M1 or M2) encodes an extracellular protein toxin (K1 or K2 toxin). Based on their densities on CsCl gradients, L-A- and M1-containing particles can be separated. Using this method, we detected a new type of M1 dsRNA-containing VLP (M1-H VLP, for heavy) that has a higher density than those previously reported (M1-L VLP, for light). M1-H and M1-L VLPs are present together in the same strains and in all those we tested. M1-H, M1-L, and L-A VLPs all have the same types of proteins in the same approximate proportions, but whereas L-A VLPs and M1-L VLPs have one dsRNA molecule per particle, M1-H VLPs contain two M1 dsRNA molecules per particle. Their RNA polymerase produces mainly plus single strands that are all extruded in the case of M1-H particles but are partially retained inside the M1-L particles to be used later for dsRNA synthesis. We show that M1-H VLPs are formed in vitro from the M1-L VLPs. We also show that the peak of M1 dsRNA synthesis is in fractions lighter than M1-L VLPs, presumably those carrying only a single plus M1 strand. We suggest that VLPs carrying two M1 dsRNAs (each 1.8 kilobases) can exist because the particle is designed to carry one L-A dsRNA (4.5 kilobases).
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Olins, A. L., D. E. Olins, and D. P. Bazett-Jones. "Balbiani ring hnRNP substructure visualized by selective staining and electron spectroscopic imaging." Journal of Cell Biology 117, no. 3 (1992): 483–91. http://dx.doi.org/10.1083/jcb.117.3.483.
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The Balbiani Rings (BR) in the polytene chromosomes of Chironomus salivary glands are intense sites of transcription. The nascent RNPs fold during transcription into 40-50-nm granules, containing in the mature transcript approximately 37-kb RNA. Using a new nucleic acid specific stain, osmium ammine B on Lowicryl sections, in combination with electron energy filtered imaging of sections containing BR granules, we demonstrate a RNA-rich particulate substructure (10-nm particle diameter; 10-12 particles per BR granule). Elemental imaging supports that these particles are enriched in phosphorus. The possible relationship of these RNA-rich particles to ribonucleosomes is discussed, as well as models for their arrangement in the mature BR granules.
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Mohammadi, Sina, and Ralph R. Isberg. "Cdc42 interacts with the exocyst complex to promote phagocytosis." Journal of Cell Biology 200, no. 1 (2013): 81–93. http://dx.doi.org/10.1083/jcb.201204090.
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The process of phagocytosis in multicellular organisms is required for homeostasis, clearance of foreign particles, and establishment of long-term immunity, yet the molecular determinants of uptake are not well characterized. Cdc42, a Rho guanosine triphosphatase, is thought to orchestrate critical actin remodeling events needed for internalization. In this paper, we show that Cdc42 controls exocytic events during phagosome formation. Cdc42 inactivation led to a selective defect in large particle phagocytosis as well as a general decrease in the rate of membrane flow to the cell surface. Supporting the connection between Cdc42 and exocytic function, we found that the overproduction of a regulator of exocytosis, Rab11, rescued the large particle uptake defect in the absence of Cdc42. Additionally, we demonstrated a temporal interaction between Cdc42 and the exocyst complex during large particle uptake. Furthermore, disruption of exocyst function through Exo70 depletion led to a defect in large particle internalization, thereby establishing a functional role for the exocyst complex during phagocytosis.
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Kressler, Dieter, Daniela Roser, Brigitte Pertschy, and Ed Hurt. "The AAA ATPase Rix7 powers progression of ribosome biogenesis by stripping Nsa1 from pre-60S particles." Journal of Cell Biology 181, no. 6 (2008): 935–44. http://dx.doi.org/10.1083/jcb.200801181.
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Ribosome biogenesis takes place successively in the nucleolar, nucleoplasmic, and cytoplasmic compartments. Numerous nonribosomal factors transiently associate with the nascent ribosomes, but the mechanisms driving ribosome formation are mostly unknown. Here, we show that an energy-consuming enzyme, the AAA-type (ATPases associated with various cellular activities) ATPase Rix7, restructures a novel pre-60S particle at the transition from the nucleolus to nucleoplasm. Rix7 interacts genetically with Nsa1 and is targeted to the Nsa1-defined preribosomal particle. In vivo, Nsa1 cannot dissociate from pre-60S particles in rix7 mutants, causing nucleolar Nsa1 to escape to the cytoplasm, where it remains associated with aberrant 60S subunits. Altogether, our data suggest that Rix7 is required for the release of Nsa1 from a discrete preribosomal particle, thereby triggering the progression of 60S ribosome biogenesis.
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Sako, Y., and A. Kusumi. "Barriers for lateral diffusion of transferrin receptor in the plasma membrane as characterized by receptor dragging by laser tweezers: fence versus tether." Journal of Cell Biology 129, no. 6 (1995): 1559–74. http://dx.doi.org/10.1083/jcb.129.6.1559.
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Our previous results indicated that the plasma membrane of cultured normal rat kidney fibroblastic cell is compartmentalized for diffusion of receptor molecules, and that long-range diffusion is the result of successive intercompartmental jumps (Sako, Y. and Kusumi, A. 1994. J. Cell Biol. 125:1251-1264). In the present study, we characterized the properties of intercompartmental boundaries by tagging transferrin receptor (TR) with either 210-nm-phi latex or 40-nm-phi colloidal gold particles, and by dragging the particle-TR complexes laterally along the plasma membrane using laser tweezers. Approximately 90% of the TR-particle complexes showed confined-type diffusion with a microscopic diffusion coefficient (Dmicro) of approximately 10(-9) cm2/s and could be dragged past the intercompartmental boundaries in their path by laser tweezers at a trapping force of 0.25 pN for gold-tagged TR and 0.8 pN for latex-tagged TR. At lower dragging forces between 0.05 and 0.1 pN, particle-TR complexes tended to escape from the laser trap at the boundaries, and such escape occurred in both the forward and backward directions of dragging. The average distance dragged was half of the confined distance of TR, which further indicates that particle-TR complexes escape at the compartment boundaries. Since variation in the particle size (40 and 210 nm, the particles are on the extracellular surface of the plasma membrane) hardly affects the diffusion rate and behavior of the particle-TR complexes at the compartment boundaries, and since treatment with cytochalasin D or vinblastin affects the movements of TR (Sako and Kusumi as cited above), argument has been advanced that the boundaries are present in the cytoplasmic domain. Rebound of the particle-TR complexes when they escape from the laser tweezers at the compartment boundaries suggests that the boundaries are elastic structures. These results are consistent with the proposal that the compartment boundaries consist of membrane skeleton or a membrane-associated part of the cytoskeleton (membrane skeleton fence model). Approximately 10% of TR exhibited slower diffusion (Dmicro approximately 10(-10)-10(-11) cm2/s) and binding to elastic structures.
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Xie, Ruo‐Chen, Maria Volokhova, Aleksei Boldin, et al. "Electrocatalytic Oxidation of Hydroxide Ions by Co 3 O 4 and Co 3 O 4 @SiO 2 Nanoparticles Both at Particle Ensembles and at the Single Particle Level." ChemElectroChem 7, no. 5 (2020): 1261–76. http://dx.doi.org/10.1002/celc.202000230.
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Rupper, A. C., J. M. Rodriguez-Paris, B. D. Grove, and J. A. Cardelli. "p110-related PI 3-kinases regulate phagosome-phagosome fusion and phagosomal pH through a PKB/Akt dependent pathway in Dictyostelium." Journal of Cell Science 114, no. 7 (2001): 1283–95. http://dx.doi.org/10.1242/jcs.114.7.1283.
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The Dictyostelium p110-related PI 3-kinases, PIK1 and PIK2, regulate the endosomal pathway and the actin cytoskeleton, but do not significantly regulate internalization of particles in D. discoideum. Bacteria internalized into (Δ)ddpik1/ddpik2 cells or cells treated with PI 3-kinase inhibitors remained intact as single particles in phagosomes with closely associated membranes after 2 hours of internalization, while in control cells, bacteria appeared degraded in multi-particle spacious phagosomes. Addition of LY294002 to control cells, after 60 minutes of chase, blocked formation of spacious phagosomes, suggesting PI 3-kinases acted late to regulate spacious phagosome formation. Phagosomes purified from control and drug treated cells contained equivalent levels of lysosomal proteins, including the proton pump complex, and were acidic, but in drug treated cells and (Δ)ddpik1/ddpik2 cells phagosomal pH was significantly more acidic during maturation than the pH of control phagosomes. Inhibition of phagosomal maturation by LY294002 was overcome by increasing phagosomal pH with NH(4)Cl, suggesting that an increase in pH might trigger homotypic phagosome fusion. A pkbA null cell line (PKB/Akt) reproduced the phenotype described for cells treated with PI 3-kinase inhibitors and (Δ)ddpik1/ddpik2 cells. We propose that PI 3-kinases, through a PKB/Akt dependent pathway, directly regulate homotypic fusion of single particle containing phagosomes to form multi-particle, spacious phagosomes, possibly through the regulation of phagosomal pH.
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Zielinski, Henryk, Ian S. Mudway, Kelly A. Bérubé, Samantha Murphy, Roy Richards, and Frank J. Kelly. "Modeling the interactions of particulates with epithelial lining fluid antioxidants." American Journal of Physiology-Lung Cellular and Molecular Physiology 277, no. 4 (1999): L719—L726. http://dx.doi.org/10.1152/ajplung.1999.277.4.l719.
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Oxidative stress may be a fundamental mode of injury associated with inspired particles. To examine this, we determined the ability of three carbon black particles (CBPs; M120, M880, and R250) and two forms of silicon dioxide, amorphous (Cabosil) and crystalline (DQ12) quartz, to deplete epithelium lining fluid antioxidant defenses. Single and composite antioxidant solutions of uric acid, ascorbic acid (AA), and reduced glutathione (GSH) were examined in the presence of particle concentrations of 150 μg/ml. Uric acid was not depleted by any particle considered. AA was depleted in a near-linear fashion with time by the three different CBPs; however, AA depletion rates varied markedly with CBP type and decreased in the presence of metal chelators. An initially high GSH depletion rate was noted with all CBPs, and this was always accompanied by the appearance of oxidized glutathione. Exposure to Cabosil or DQ12 did not result in the loss of GSH. Together, these data demonstrate that particle type, size, and surface area are all important factors when considering particle-antioxidant interactions in the airways.
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Wilson, K. M., I. E. Morrison, P. R. Smith, N. Fernandez, and R. J. Cherry. "Single particle tracking of cell-surface HLA-DR molecules using R-phycoerythrin labeled monoclonal antibodies and fluorescence digital imaging." Journal of Cell Science 109, no. 8 (1996): 2101–9. http://dx.doi.org/10.1242/jcs.109.8.2101.
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The mobility of cell surface MHC molecules and their ability to form dynamic associations may be related to the physiological status of the cell and to the potential to bind effector T lymphocytes. To investigate these properties, we have prepared HLA DR specific monoclonal antibodies coupled in a 1:1 mole ratio to the fluorescent phycobiliprotein, R-phycoerythrin (PE). We show that these small particles can be sequentially imaged using a cooled slow-scan charge coupled device camera and hence can be used for single particle tracking experiments. We have applied this technique to investigate the movements of HLA DR molecules on fibroblasts transfected with human DR alpha and DR beta genes. PE-IgG was bound to the transfected fibroblasts and particle tracks were obtained by sequential imaging over a period of typically 30 minutes. Analysis of particle tracks revealed the presence of directed motion and domain-limited diffusion in addition to random diffusion. The contributions of these three types of motion showed cell to cell variability. Velocities of directed motion were of the order of 2 nm second-1 whilst domain diameters were in the range 200–800 nm. Diffusion coefficients for random diffusion were in the range 1 × 10(−13)-5 × 10(−12) cm2 second-1. The higher mobilities were observed for the lower intensity fluorescent spots, which possibly correspond to images of single particles. Much lower mobility was observed with a cell where the spot intensities were approximately double that of the lower intensity spots. These spots could be images of double particles implying the association of at least two HLA DR alpha beta dimers. These data are relevant to the study of MHC class II cell surface redistribution and antigen presentation in specific immunity.
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Newman, R., G. W. Butcher, B. Bullard, and K. R. Leonard. "A method for determining the periodicity of a troponin component in isolated insect flight muscle thin filaments by gold/Fab labelling." Journal of Cell Science 101, no. 3 (1992): 503–8. http://dx.doi.org/10.1242/jcs.101.3.503.
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Insect flight muscle has a large component (Tn-H) in the tropomyosin-troponin complex that is not present in vertebrate striated muscle thin filaments. Tn-H is shown by gold/Fab labelling to be present at regular intervals in insect flight muscle thin filaments. The Fab fragment of a monoclonal antibody to Tn-H was conjugated directly with colloidal gold and this probe used to label isolated thin filaments from the flight muscle of Lethocerus indicus (water bug). The distribution of gold particles seen in electron microscope images of negatively stained thin filaments was analysed to show that the probe bound to sites having a periodicity of approximately 40 nm, which is the expected value for the tropomyosin-troponin repeat. Conjugates of Fab with colloidal gold particles of 3 nm diameter labelled almost all sites. Conjugates with gold particles of 5 nm and 10 nm diameter labelled less efficiently (70% and 30%, respectively) but analysis of the distribution of inter-particle intervals among a number of filaments again gave the same fundamental spacing of 40 nm. The error in the measurements (standard deviation approximately +/− 4.2 for 5 nm gold/Fab) is less than earlier estimates for the size of the gold/Fab complex. Measurements on gold/Fab in negative stain suggest that the bound Fab contributes a shell about 2 nm in thickness around the gold particle. The radius of the probe (about 4.5 nm for 5 nm gold/Fab) would then be consistent with the value of error found. The size of the probe suggests that the gold particle binds to the side of the Fab molecule, rather close to the antibody combining site. The potential resolution of the technique may thus be better than originally expected.
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Lindberg, F. P., H. D. Gresham, M. I. Reinhold, and E. J. Brown. "Integrin-associated protein immunoglobulin domain is necessary for efficient vitronectin bead binding." Journal of Cell Biology 134, no. 5 (1996): 1313–22. http://dx.doi.org/10.1083/jcb.134.5.1313.
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Integrin-associated protein (IAP/CD47) is physically associated with the alpha v beta 3 vitronectin (Vn) receptor and a functionally and immunologically related integrin on neutrophils (PMN) and monocytes. Anti-IAP antibodies inhibit multiple phagocyte functions, including Arg-Gly-Asp (RGD)-initiated activation of phagocytosis, chemotaxis, and respiratory burst; PMN adhesion to entactin; and PMN transendothelial and transepithelial migration at a step subsequent to tight intercellular adhesion. Anti-IAP antibodies also inhibit binding of Vn-coated particles to many cells expressing alpha v beta 3. However, prior studies with anti-IAP did not directly address IAP function because they could not distinguish between IAP blockade and antibody-induced signaling effects on cells. To better determine the function of IAP, we have characterized and used an IAP-deficient human cell line. Despite expressing alpha v integrins, these cells do not bind Vn-coated particles unless transfected with IAP expression constructs. Increasing the level of alpha v beta 3 expression or increasing Vn density on the particle does not overcome the requirement for IAP. All known splice variants of IAP restore Vn particle binding equivalently. Indeed, the membrane-anchored IAP Ig variable domain suffices to mediate Vn particle binding in this system, while the multiply membrane-spanning and cytoplasmic domains are dispensable. In all cases, adhesion to a Vn-coated surface and fibronectin particle binding through alpha 5 beta 1 fibronectin receptors are independent of IAP expression. These data demonstrate that some alpha v integrin ligand-binding functions are IAP independent, whereas others require IAP, presumably through direct physical interaction between its Ig domain and the integrin.
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Grainger, J. L., and M. M. Winkler. "The sea urchin multicatalytic protease: purification, biochemical analysis, subcellular distribution, and relationship to snRNPs." Journal of Cell Biology 109, no. 2 (1989): 675–83. http://dx.doi.org/10.1083/jcb.109.2.675.
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We have purified and extensively characterized a 19-S particle from sea urchin eggs. This particle is the sea urchin homologue of the "prosome", a particle originally identified in duck erythroblasts. We now show that these sea urchin prosomes contain multiple proteolytic activities. As shown for analogous particles from other cells, these particles hydrolyze synthetic substrates containing neutral hydrophobic or basic amino acids at the carboxy terminus of the synthetic peptides. They contain 16-20 small proteins ranging in molecular weight from 20,000 to 32,000. Peptide mapping shows that most of the polypeptides are unique, however, three exist in two isoelectric forms. We have investigated the possible function of the sea urchin multicatalytic proteases (MCPs) by determining their subcellular distribution, their relationship to egg snRNPs, and their possible role in translational repression. There are almost as many MCPs (2 x 10(8] as ribosomes (6.6 x 10(8] or mRNPs (1.8 x 10(7] per egg. This suggests that like ribosomes, the MCPs are stored in the egg for use during later development. We find that a substantial proportion of egg MCPs move into nuclei by the late blastula stage. Using a specific antibody against one of the sea urchin MCP proteins and antibodies against U1-U6, La, and Ro RNPs, we show that the sea urchin particle is distinct from these RNPs, although the anti-U1-U6 RNP antibody cross-reacts with a single MCP protein. In addition, the sea urchin MCP appears to be associated with a large structure in the cytoplasm of unfertilized eggs and is released under the same conditions that activate egg mRNPs in vitro.
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Yang, Lu-Ying, and Arnis Kuksis. "Size and composition of lymph chylomicrons following feeding corn oil or its fatty acid methyl esters." Biochemistry and Cell Biology 65, no. 6 (1987): 514–24. http://dx.doi.org/10.1139/o87-066.
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Male rats with thoracic duct cannulae were intubated with com oil or fatty acid methyl esters and the lymph was collected over the next 2–72 h. The apoprotein (apo) composition of the chylomicrons, isolated by conventional ultracentrifugation, was determined by sodium dodecyl sulfate – polyacrylamide – glycerol gel electrophoresis and isoelectric focusing. The lipid content and composition was assessed by gas–liquid chromatography. The particle size was obtained by calculation and confirmed by electron microscopy. The study demonstrates that both the monoacylglycerol (corn oil feeding) and the phosphatidic acid (methyl ester feeding) pathways of triacylglycerol biosynthesis yield chylomicrons with closely similar apoprotein profiles representing apo B-48, apo A-IV, apo E, apo A-I, and the apo C components. A protein band corresponding to apo B-100 was occasionally observed as a minor component of the chylomicrons from both groups of animals. The chylomicrons from com oil feeding had about two times larger diameters than those from methyl ester feeding. There were no significant differences in the composition of the apoproteins, although the smaller particles had two times higher apoprotein/triacylglycerol ratios. It was calculated that the amount of apo B per lipid particle for the ester fed rats ranged from one to eight molecules and was closely correlated with the particle size. The corn oil fed rats yielded about three molecules apo B per lipid particle regardless of the particle size. It is concluded that the pathway of intestinal triacylglycerol biosynthesis has a significant effect on the apoprotein mass and to a lesser extent on the apoprotein and lipid composition of the chylomicrons. The phosphatidic acid pathway produces smaller particles and transfers to the bloodstream twice as much apoprotein per gram of fat than the monoacylglycerol pathway, which yields the larger particles. Possible variations in the site and rate of biosynthesis of the triacylglycerols could not be entirely excluded as contributing factors.
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Flannagan, Ronald S., Rene E. Harrison, Christopher M. Yip, Khuloud Jaqaman, and Sergio Grinstein. "Dynamic macrophage “probing” is required for the efficient capture of phagocytic targets." Journal of Cell Biology 191, no. 6 (2010): 1205–18. http://dx.doi.org/10.1083/jcb.201007056.
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Binding of ligands by immunoreceptors is thought to be a passive, stochastic process. Contrary to this notion, we found that binding of IgG-opsonized particles by Fcγ receptors was inhibited in macrophages, dendritic and microglial cells by agents that interfere with actin assembly or disassembly. Changes in the lateral mobility of the receptors—assessed by single-particle tracking—or in the microelasticity of the membrane—determined by atomic-force microscopy—could not account for the effects of actin disruption on particle binding. Instead, we found that the macrophages contact their targets by actively extending actin-rich structures. Formation of these protrusions is driven by Rac and requires phosphatidylinositol 4,5-bisphosphate and phosphatidylinositol 3,4,5-trisphosphate. Capture of C3bi-opsonized as well as unopsonized targets by macrophages was also dependent on actin. Thus, phagocytes continuously probe their environment for foreign particles in a manner akin to the constitutive sampling of the fluid milieu by dendritic cells. Active probing by phagocytes is most important when confronted by scarcely opsonized and/or highly mobile targets.
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Yu, Zhi, Michael Grafe, Heike Meyborg, Eckart Fleck, and Yangqiu Li. "In Vitro Characterization of Magnetic Resonance Imaging Contrast Agents for Molecular Imaging." Blood 108, no. 11 (2006): 3944. http://dx.doi.org/10.1182/blood.v108.11.3944.3944.
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Abstract The aim of this work was to evaluate the biological properties of one citrate-coated and two different dextran-coated paramagnetic particles with comparable size (iron core 4–10 nm). Endothelial cells from humans and mice as well as human macrophages were incubated for different time intervals with different particle suspensions. The cellular uptake was semi-quantitatively measured using the Prussian blue staining and, in addition, by cellular iron content. Furthermore the effect of known inhibitors of endocytosis was evaluated. In addition, it was evaluated whether linking of monoclonal antibodies to dextran-coated particles can make them bind specifically to certain cell surface structures. The results showed that the bEnd.3 cell line, human umbilical vein endothelial cells (HUVECs) and THP-1/macrophage cell lines internalize paramagnetic particles. The ranking of cellular uptake was: VSOP &gt; CMD-coated particles &gt;&gt; CLIO. The carboxydextran-coated SPIO uptake by endothelial cells is reduced by colchicine (50%). Conversely, cytochalasin B down-regulates the endocytosis of citrate-coated particle. Our data imply that the major mechanism of uptake would be pinocytosis for the VSOP and phagocytosis for the carboxydextran-coated particle CMD. The different surface coating can influence not only the quantity of the internalization, but also the pathway of internalization. CLIO linked to CD40 antibodies or to CD62E antibodies bound significantly better than IgG-linked CLIO. This was true especially for the anti-CD40-CLIO constructs where fluorescence increased two fold. Comparable results were observed with anti-CD62E-CLIO constructs; however, increase in fluorescence was higher than with CD40 binding; it increased on 3.9-fold (median) and 4.5-fold (mean). In conclusions, the binding of antibody-conjugated CLIO to the antigen-expressing cells was specific, with an affinity similar to that of the free antibody. Thus, it seems feasible to use antibody linked SPIOs for molecular imaging.
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S. K. Dhakad, S. K. Dhakad, Dr S. C. Soni Dr. S.C. Soni, and Dr Pankaj Agarwal. "Cross Validation of Optimize Results Using Genetic and Particle Swarm Optimization (PSO) Algorithms, for the Single Cell Model of Molten Carbonate Fuel Cell (MCFC)." International Journal of Scientific Research 2, no. 4 (2012): 30–31. http://dx.doi.org/10.15373/22778179/apr2013/44.
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Paul, Dilip K., Kejie Meng, Dario Omanovic, and Julio C. Alvarez. "Hydrogen Bonding and Proton Transfer in Aqueous Toluene Microdroplets Studied by Particle Collision Electrochemistry." ChemElectroChem 5, no. 18 (2018): 2528–33. http://dx.doi.org/10.1002/celc.201800542.
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Öhl, Denis, Jan Clausmeyer, Stefan Barwe, Alexander Botz, and Wolfgang Schuhmann. "Oxygen Reduction Activity and Reversible Deactivation of Single Silver Nanoparticles during Particle Adsorption Events." ChemElectroChem 5, no. 14 (2018): 1886–90. http://dx.doi.org/10.1002/celc.201800094.
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