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Electron Microscopy Analysis (electron + microscopy_analysis)
Kinds of Electron Microscopy Analysis Selected AbstractsSignalling mechanisms for Toll-like receptor-activated neutrophil exocytosis: key roles for interleukin-1-receptor-associated kinase-4 and phosphatidylinositol 3-kinase but not Toll/IL-1 receptor (TIR) domain-containing adaptor inducing IFN-, (TRIF)IMMUNOLOGY, Issue 3 2009Agnieszka A. Brzezinska Summary Lipopolysaccharide (LPS) stimulates exocytosis in neutrophils. The signalling molecules involved in the regulation of this mechanism are currently unknown. Using neutrophils from interleukin-1-receptor-associated kinase (IRAK)-4- and Toll/IL-1 receptor (TIR) domain-containing adaptor inducing IFN-, (TRIF)-deficient mice, we dissected the signalling pathways that control exocytosis. We analysed exocytosis of peroxidase-negative and azurophilic granules by following the mobilization of the ,2-integrin subunit CD11b and myeloperoxidase (MPO)-containing granules, respectively. IRAK-4-null neutrophils showed marked defects in both peroxidase-negative and azurophilic granule exocytosis in response to LPS. In contrast, the exocytic response to LPS of TRIF-deficient neutrophils was not different from that of wild-type cells. No differences were observed in the exocytosis of secretory organelles between IRAK-4-null and wild-type neutrophils when they were stimulated with the phorbol ester phorbol 12-myristate 13-acetate (PMA). Electron microscopy analysis showed that no morphological abnormalities were present in the granules of IRAK-4-deficient neutrophils, suggesting that the lack of exocytic response to LPS is not attributable to developmental abnormalities. Using pharmacological inhibitors, we found that p38 mitogen-activated protein kinase (p38MAPK) is essential for the exocytosis of all neutrophil secretory organelles in response to LPS. Interestingly, we found that phosphatidylinositol 3-kinase (PI3K) is essential for azurophilic granule exocytosis but not for the mobilization of other neutrophil granules in response to LPS. Azurophilic granule exocytosis in response to Listeria monocytogenes was dependent on PI3K but not IRAK-4 activity, suggesting that alternative signalling pathways are activated in IRAK-4-deficient neutrophils exposed to whole bacteria. Our results identified IRAK-4, p38MAPK and PI3K as important regulatory components with different roles in the signalling pathways that control Toll-like receptor ligand-triggered neutrophil exocytosis. [source] Electron microscopy analysis of histone acetylation and DNA strand breaks in mouse elongating spermatids using a dual labelling approachANDROLOGIA, Issue 5 2010G. Bikond Nkoma Summary Chromatin remodelling steps in mammalian spermatids include post-translational modifications of histones and DNA fragmentation. Histone H4 hyperacetylation (AcH4) establishes a chromatin state that facilitates DNA repair in somatic cells. So we sought to determine whether a similar link exists in spermatids by combining immunogold labelling with detection of DNA strand breaks, making use of gold particles of different sizes. DNA strand breaks were not detected in the vicinity of AcH4 chromatin, suggesting that this modified histone may not be involved in the aetiology of DNA fragmentation and repair in spermatids. The AcH4 reactivity, however, indicates that chromatin remodelling is distributed throughout the nucleus. [source] Widespread occurrence of an intranuclear bacterial parasite in vent and seep bathymodiolin musselsENVIRONMENTAL MICROBIOLOGY, Issue 5 2009Frank U. Zielinski Summary Many parasitic bacteria live in the cytoplasm of multicellular animals, but only a few are known to regularly invade their nuclei. In this study, we describe the novel bacterial parasite "Candidatus Endonucleobacter bathymodioli" that invades the nuclei of deep-sea bathymodiolin mussels from hydrothermal vents and cold seeps. Bathymodiolin mussels are well known for their symbiotic associations with sulfur- and methane-oxidizing bacteria. In contrast, the parasitic bacteria of vent and seep animals have received little attention despite their potential importance for deep-sea ecosystems. We first discovered the intranuclear parasite "Ca. E. bathymodioli" in Bathymodiolus puteoserpentis from the Logatchev hydrothermal vent field on the Mid-Atlantic Ridge. Using primers and probes specific to "Ca. E. bathymodioli" we found this intranuclear parasite in at least six other bathymodiolin species from vents and seeps around the world. Fluorescence in situ hybridization and transmission electron microscopy analyses of the developmental cycle of "Ca. E. bathymodioli" showed that the infection of a nucleus begins with a single rod-shaped bacterium which grows to an unseptated filament of up to 20 ,m length and then divides repeatedly until the nucleus is filled with up to 80 000 bacteria. The greatly swollen nucleus destroys its host cell and the bacteria are released after the nuclear membrane bursts. Intriguingly, the only nuclei that were never infected by "Ca. E. bathymodioli" were those of the gill bacteriocytes. These cells contain the symbiotic sulfur- and methane-oxidizing bacteria, suggesting that the mussel symbionts can protect their host nuclei against the parasite. Phylogenetic analyses showed that the "Ca. E. bathymodioli" belongs to a monophyletic clade of Gammaproteobacteria associated with marine metazoans as diverse as sponges, corals, bivalves, gastropods, echinoderms, ascidians and fish. We hypothesize that many of the sequences from this clade originated from intranuclear bacteria, and that these are widespread in marine invertebrates. [source] Microstructure of Nanocrystalline Yttria-Doped Zirconia Thin Films Obtained by Sol,Gel ProcessingJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 7 2008Benjamin Butz Nano- and microcrystalline yttria-stabilized zirconia (YSZ) thin films with a dopant concentration of 8.3±0.3 mol% Y2O3 were prepared with a variation in grain size by two orders of magnitude. A sol,gel-based method with consecutive rapid thermal annealing was applied to fabricate YSZ films, resulting in about 400 nm YSZ on sapphire substrates. The average grain sizes were varied between 5 nm and 0.5 ,m by heat treatment in the temperature range of 650°,1350°C for 24 h. High-resolution (HRTEM) and conventional transmission electron microscopy analyses confirmed specimens,irrespective of the thermal treatment,consisting of cubic (c -)ZrO2 grains with nanoscaled tetragonal precipitates coherently embedded in the cubic matrix. Energy-dispersive X-ray spectroscopy and HRTEM on a large number of specimens yielded a homogeneous yttria concentration within the grains and at the grain boundaries with the absence of impurities, i.e. silica at the grain boundaries. [source] Synthesis and Properties of Porous Single-Phase ,,-SiAlON CeramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 7 2002Jian-Feng Yang Single-phase ,,-SiAlON (Si6,zAlzOzN8,z, z= 0,4.2) ceramics with porous structure have been prepared by pressureless sintering of powder mixtures of á-Si3N4, AlN, and Al2O3 of the SiAlON compositions. A solution of AlN and Al2O3 into Si3N4 resulted in the ,,-SiAlON, and full densification was prohibited because no other sintering additives were used. Relative densities ranging from 50%,90% were adjusted with the z -value and sintering temperature. The results of X-ray diffraction, scanning electron microscopy, and transmission electron microscopy analyses indicated that single-phase ,,-SiAlON free from a grain boundary glassy phase could be obtained. Both grain and pore sizes increased with increasing z -value. Low z -value resulted in a relatively high flexural strength. [source] Biosynthesis of Sb2O3 nanoparticles: A low-cost green approachBIOTECHNOLOGY JOURNAL, Issue 11 2009Anal K. Jha Abstract A low-cost green and reproducible microbe (Lactobacillus sp.)-mediated biosynthesis of Sb2O3 nanoparticles is reported. The synthesis was performed at around room temperature. X-ray and transmission electron microscopy analyses were performed to ascertain the formation of Sb2O3 nanoparticles. X-ray analysis indicated that Sb2O3 nanoparticles had a face-centered cubic unit cell structure. Individual nanoparticles as well as a few aggregates of 3,12 nm were found. A possible mechanism for the synthesis of nano Sb2O3 is proposed. [source] Biosynthesis of silver nanoparticles using Eclipta leafBIOTECHNOLOGY PROGRESS, Issue 5 2009Anal K. Jha Abstract A green, low-cost and reproducible Eclipta leaves negotiated synthesis of silver nanoparticles is reported. The synthesis is performed at room temperature. X-ray and transmission electron microscopy analyses are performed to ascertain the formation of Ag nanoparticles. Nanoparticles almost spherical in shape having a size of 2,6 nm are found. UV-visible study revealed the surface plasmon resonance at 419 nm. The lattice strain is estimated to be 0.0045 using Williamson-Hall approach. The use of Eclipta for the synthesis of silver nanoparticles offers the benefit of ecofriendliness and amenability for large scale production through scaling up. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009 [source] Synchrotron X-ray reflectivity studies of nanoporous organosilicate thin films with low dielectric constantsJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 2007Weontae Oh Quantitative, non-destructive X-ray reflectivity analysis using synchrotron radiation sources was successfully performed on nanoporous dielectric thin films prepared by thermal processing of blend films of a thermally curable polymethylsilsesquioxane dielectric precursor and a thermally labile triethoxysilyl-terminated six-arm poly(,-caprolactone) porogen in various compositions. In addition, thermogravimetric analysis and transmission electron microscopy analysis were carried out. These measurements provided important structural information about the nanoporous films. The thermal process used in this study was found to cause the porogen molecules to undergo efficiently sacrificial thermal degradation, generating closed, spherical nanopores in the dielectric film. The resultant nanoporous films exhibited a homogeneous, well defined structure with a thin skin layer and low surface roughness. In particular, no skin layer was formed in the porous film imprinted using a porogen loading of 30,wt%. The film porosities ranged from 0 to 33.8% over the porogen loading range of 0,30,wt%. [source] Increased Bone Formation in Mice Lacking Plasminogen Activators,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 7 2003E Daci Abstract Plasminogen activators tPA and uPA are involved in tissue remodeling, but their role in bone growth is undefined. Mice lacking tPA and uPA show increased bone formation and bone mass. The noncollagenous components of bone matrix are also increased, probably from defective degradation. This study underlines the importance of controlled bone matrix remodeling for normal endochondral ossification. Introduction: Proteolytic pathways are suggested to play a role in endochondral ossification. To elucidate the involvement of the plasminogen activators tPA and uPA in this process, we characterized the long bone phenotype in mice deficient in both tPA and uPA (tPA,/,:uPA,/,). Materials and Methods: Bones of 2- to 7-day-old tPA,/,:uPA,/, and wild-type (WT) mice were studied using bone histomorphometry, electron microscopy analysis, and biochemical assessment of bone matrix components. Cell-mediated degradation of metabolically labeled bone matrix, osteoblast proliferation, and osteoblast differentiation, both at the gene and protein level, were studied in vitro using cells derived from both genotypes. Results: Deficiency of the plasminogen activators led to elongation of the bones and to increased bone mass (25% more trabecular bone in the proximal tibial metaphysis), without altering the morphology of the growth plate. In addition, the composition of bone matrix was modified in plasminogen activator deficient mice, because an increased amount of proteoglycans (2×), osteocalcin (+45%), and fibronectin (+36%) was detected. Matrix degradation assays showed that plasminogen activators, by generating plasmin, participate in osteoblast-mediated degradation of the noncollagenous components of bone matrix. In addition, proliferation of primary osteoblasts derived from plasminogen activator-deficient mice was increased by 35%. Finally, osteoblast differentiation and formation of a mineralized bone matrix were enhanced in osteoblast cultures derived from tPA,/,:uPA,/, mice. Conclusions: The data presented indicate the importance of the plasminogen system in degradation of the noncollagenous components of bone matrix and suggest that the accumulation of these proteins in bone matrix,as occurs during plasminogen activator deficiency,may in turn stimulate osteoblast function, resulting in increased bone formation. [source] Nuclear changes in necrotic HL-60 cellsJOURNAL OF CELLULAR BIOCHEMISTRY, Issue S36 2001Roberta Bortul Abstract Cell death in eukaryotes can occur by either apoptosis or necrosis. Apoptosis is characterized by well-defined nuclear changes which are thought to be the consequence of both proteolysis and DNA fragmentation. On the other hand, the nuclear modifications that occur during necrosis are largely less known. Here, we have investigated whether or not nuclear modifications occur during ethanol-induced necrotic cell death of HL-60 cells. By means of immunofluorescence staining, we demonstrate that the patterns given by antibodies directed against some nuclear proteins (lamin B1, NuMA, topoisomerase II,, SC-35, B23/nucleophosmin) changed in necrotic cells. The changes in the spatial distribution of NuMA strongly resembled those described to occur during apoptosis. On the contrary, the fluorescent pattern characteristic for other nuclear proteins (C23/nucleolin, UBF, fibrillarin, RNA polymerase I) did not change during necrosis. By immunoblotting analysis, we observed that some nuclear proteins (SAF-A, SATB1, NuMA) were cleaved during necrosis, and in the case of SATB1, the apoptotic signature fragment of 70 kDa was also present to the same extent in necrotic samples. Caspase inhibitors did not prevent proteolytic cleavage of the aforementioned polypeptides during necrosis, while they were effective if apoptosis was induced. In contrast, lamin B1 and topoisomerase II, were uncleaved in necrotic cells, whereas they were proteolyzed during apoptosis. Transmission electron microscopy analysis revealed that slight morphological changes were present in the nuclear matrix fraction prepared from necrotic cells. However, these modifications (mainly consisting of a rarefaction of the inner fibrogranular network) were not as striking as those we have previously described in apoptotic HL-60 cells. Taken together, our results indicate that during necrosis marked biochemical and morphological changes do occur at the nuclear level. These alterations are quite distinct from those known to take place during apoptosis. Our results identify additional biochemical and morphological criteria that could be used to discriminate between the two types of cell death. J. Cell. Biochem. Suppl. 36: 19,31, 2001. © 2001 Wiley-Liss, Inc. [source] First combined electron backscatter diffraction and transmission electron microscopy study of grain boundary structure of deformed quartziteJOURNAL OF MICROSCOPY, Issue 3 2006N. SHIGEMATSU Summary The structures of boundaries in a deformed and dynamically recovered and recrystallized quartz polycrystal (mylonite) were characterized by transmission electron microscopy, after the misorientation angles across the same grain boundaries had been analysed using electron backscatter diffraction in a scanning electron microscope. In this new approach, a specific sample area is mapped with electron backscatter diffraction, and the mapped area is then attached to a foil, and by the ion beam thinned for transmission electron microscopy analysis. Dislocations in grain boundaries were recognized as periodic and parallel fringes. The fringes associated with dislocations are observed in boundaries with misorientations less than 9°, whereas such fringes cannot be seen in the boundaries with misorientations larger than 17°. Some boundaries with misorientations between 9° and 17° generally have no structures associated with dislocation. One segment of a boundary with a misorientation of 13.5° has structures associated with dislocations. It is likely that the transition from low-angle to high-angle boundaries occurs at misorientations ranging from approximately 9° to 14°. Change in the grain boundary structure presumably influences the mobility of the boundaries. In the studied deformed quartz vein, a relative dearth of boundaries between misorientation angles of , = 2° and , = 15° has previously been reported, and high-angle boundaries form cusps where they intersect low-angle boundaries, suggesting substantial mobility of high-angle boundaries. [source] A simple method for SEM examination of sectioned diatom frustulesJOURNAL OF MICROSCOPY, Issue 1 2001SHORT TECHNICAL NOTE We describe an innovative yet straightforward method to obtain high quality thin sections of diatom exoskeletons for observation by scanning electron microscopy (SEM). The use of this new technique allows for clear observations of some ultrastructural valve features, including the raphe, which are generally difficult to observe and describe accurately using transmission electron microscopy analysis of thin sections or SEM of randomly fractured diatom valves. In addition, because this method involves the complete removal of the organic content of the diatom cells, resulting in clean and mostly undisturbed skeletal thin cross-sections, even the intact valvar structures of weak girdle bands can be studied. [source] Glial-guided neuronal migration in P19 embryonal carcinoma stem cell aggregatesJOURNAL OF NEUROSCIENCE RESEARCH, Issue 1 2005Marcelo F. Santiago Abstract During development of the nervous system, neuronal precursors that originated in proliferative regions migrate along radial glial fibers to reach their final destination. P19 embryonal carcinoma (EC) stem cells exposed to retinoic acid (RA) differentiate into neurons, glia, and fibroblast-like cells. In this work, we induced P19 aggregates for 4 days with RA and plated them onto tissue culture dishes coated with poly-L-lysine. Several cells migrated out of and/or extended processes from the aggregates after 24 hr. Some cell processes were morphologically similar to radial glial fibers and stained for glial fibrillar acidic protein (GFAP) and nestin. Large numbers of migrating cells showed characteristics similar to those of bipolar migrating neurons and expressed the neuronal marker microtubule-associated protein 2. Furthermore, scanning electron microscopy analysis revealed an intimate association between the radial fibers and the migrating cells. Therefore, the migration of neuron-like cells on radial glia fibers in differentiated P19 aggregates resembled some of the migration models used thus far to study gliophilic neuronal migration. In addition, HPTLC analysis in this system showed the expression of 9-O-acetyl GD3, a ganglioside that has been associated with neuronal migration. Antibody perturbation assays showed that immunoblockage of 9-O-acetyl GD3 arrested neuronal migration in a reversible manner. In summary, we have characterized a new cell culture model for investigation of glial-guided neuronal migration and have shown that 9-O-acetyl GD3 ganglioside has an important role in this phenomenon. © 2005 Wiley-Liss, Inc. [source] Microwave Dielectric Properties of Ba3(VO4)2,Mg2SiO4 Composite CeramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 2 2010Siqin Meng Novel Ba3(VO4)2,Mg2SiO4 microwave dielectric composite ceramics with compositions of (1,x)Ba3(VO4)2,xMg2SiO4 (x=0.50,0.65) have been prepared by firing mixtures of Ba3(VO4)2 and Mg2SiO4. X-ray diffraction and scanning electron microscopy analysis revealed that they coexist without forming secondary phases. Because their resonant frequency temperature coefficients (,f) have opposite signs, the ,f of the composite ceramic can be adjusted passing through zero by changing the relative content of the two phases. Dielectric property measurements were performed using the resonator method at around 11 GHz. Ceramics with Mg2SiO4 55 wt% sintered at 1175°C exhibited microwave dielectric properties of dielectric constant ,r=9.03, Q×f=52 500 GHz, and ,f=0.6 ppm/°C at 11.3 GHz. In this composite ceramic, we observed that the formation of the MgSiO3 secondary phase was suppressed. [source] Formation of Ceramics from Metakaolin-Based Geopolymers: Part I,Cs-Based GeopolymerJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 1 2009Jonathan L. Bell The structural evolution and crystallization of a cesium-based geopolymer (Cs2O·Al2O3·4SiO2·11H2O) on heating was studied by a variety of techniques including X-ray diffraction, thermal analysis, dilatometry, pycnometry, specific surface area, and microstructural investigation. The Cs geopolymer gradually crystallized into pollucite (Cs2O·Al2O3·4SiO2) on heating above 900°C. Its low crystallization temperature is believed to be due to the presence of nuclei in the geopolymer precursor, which are formed after curing at 50°C for 24 h. The Cs-based geopolymer was found to be more refractory compared with K- and Na-based geopolymers. Significant shrinkage, due primarily to viscous sintering, did not occur until the samples were heated to above 1200°C. The microstructure of unheated geopolymer had ,20,30 nm-sized precipitates that coarsened on heating above 1000°C. By 1350°C, the geopolymer surface had a smooth, glassy texture, although large macropores and closed pores remained. After heating to 1600°C, the closed pores were removed, and the geopolymer reached ,98% of the theoretical density of pollucite. Higher than expected levels of Cs were found near large voids, as seen by scanning electron microscopy and transmission electron microscopy analysis. The presence of this extra Cs was due to Cs left behind in pore water, which was not bound within the geopolymer structure. [source] On-Site Fabrication of Crystalline Cerium Oxide Films and Patterns by Ink-Jet Deposition Method at Moderate TemperaturesJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 7 2008Ruwan Gallage Crystalline CeO2 films and patterns have been successfully fabricated in a "single-step process" at moderate temperature. In this process, the combination of the ink-jet technique and depositing the precursor on a hot substrate (,300°C) gave crystalline CeO2 without further heat treatment. X-ray diffraction analysis revealed that the phase formed was crystallized ceria with nanosized (<10 nm) crystallites. The film thickness was several hundred nanometers and the pattern width was about 150 ,m. Scanning electron microscopy analysis showed that the films and patterns were free of cracks and adhered to the substrate. This is the first report about the direct patterning of crystalline CeO2 without postfiring or posttreatments like masking, etching, etc. [source] The preparation and properties of dextrin-graft-acrylic acid/montmorillonite superabsorbent nanocompositePOLYMER COMPOSITES, Issue 7 2009Xin Ding A novel superabsorbent nanocomposite was synthesized through intercalation polymerization of partially neutralized acrylic acid, gelatinized dextrin, and an organic-montmorillonite powder using N,N -methylenebisacrylamide as a crosslinker, Span-60 as a dispersant, and ammonium persulfate together with sodiumsulfite as a type of mixed redox initiator. Effects of the amount of them on water absorbency of the superabsorbent were investigated. The structure and the morphology of the nanocomposite were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, and transmission electron microscopy analysis. The blood compatibility of the composite was primarily measured. The results show that the acrylic acid monomer was successfully intercalated into the organic-montmorillonite layers and bonded with them. The superabsorbent nanocomposite synthesized under optimal conditions with an organic-montmorillonite powder content of 5 wt% exhibit an absorption of 725.3 g/g in distilled water and favorable blood compatibility. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers [source] Biodegradable nanocomposites from maleated polycaprolactone/soy protein isolate blend with organoclay: Preparation, characterization, and propertiesPOLYMER COMPOSITES, Issue 6 2009Abhisek Sasmal New biobased, eco-friendly nanocomposites were prepared from maleated polycaprolactone/soy protein isolate blend (50/50 wt/wt) with organo-modified clay by melt compounding. The XRD, TEM, tensile, DMTA, and rheological properties of the nanocomposites were investigated. X-ray diffraction and transmission electron microscopy analysis revealed that the intercalated nanocomposite is formed and the silicate layers of the clay are uniformly dispersed at a nanometer scale in the polymer matrix. There is a great enhancement in tensile and dynamic mechanical properties of the nanocomposites. Rheological study revealed that the nanocomposite exhibits strong shear thinning behavior and clay particles form network in the melted state of the composites. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers [source] Thermal and mechanical properties of a hydroxyl-functional dendritic hyperbranched polymer and trifunctional epoxy resin blendsPOLYMER ENGINEERING & SCIENCE, Issue 10 2001D. Ratna Curing characteristics of blends of a hydroxyl-functionalized dendritic hyperbranched polymer (HBP) and a triglycidyl p-amino phenol (TGAP) epoxy resin have been studied. THe HBP strongly enhances the curing rate owing to the catalytic effect of the hydroxyl groups. THe thermal and dynamic viscoelastic behavior of the blends of various compositions (HBP content 0,20%) have been examined and compared to the neat TGAP matrix. THe glass transition temperature (Tg) gradually decreases with increase in HBP concentration. The blends show a higher impact strength compared to neat TGAP. Scanning electron microscopy analysis indicates a single-phase morphology. [source] Spongy Polyethersulfone Membrane for Hepatocyte Cultivation: Studies on Human Hepatoma C3A CellsARTIFICIAL ORGANS, Issue 9 2008Andrzej Kinasiewicz Abstract:, There are different types of membranes used for hepatocyte cultivation. In our studies, spongy polyethersulfone (PES) membranes were examined as a support for hepatic cell cultivation in vitro. The extended surface of the membranes allows to introduce a high cell number especially in three-dimensional gel structure. Scanning electron microscopy analysis indicated that C3A cells used in our experiments grew well on PES membranes forming microvilli characteristic for normal hepatocytes. Analysis of cell viability proved that spongy PES membrane is well tolerated by J774 macrophages and did not stimulate nitric oxide synthesis. Bile canalicular structures were observed in fluorescence microscopy after F-actin staining with tetramethyl rhodamine iso-thiocyanate (TRITC)-phalloidin. The C3A cells showed high affinity to the PES membranes and adhered to almost 90% during the initial 24 h of incubation. Albumin production increased during static culture from the value of 805.2 ± 284.4 (ng/24 h/initial 106 cells) during the first days, to 2017.6 ± 505.9 (ng/24 h/initial 106 cells) after 10 days of culture. In conclusion, the spongy PES membranes can be used as scaffold for hepatocyte cultivation, especially for the creation of three-dimensional environments. [source] Antithrombogenic Polynitrosated Polyester/Poly(methyl methacrylate) Blend for the Coating of Blood-Contacting SurfacesARTIFICIAL ORGANS, Issue 4 2008Amedea B. Seabra Abstract:, A nitric oxide (NO) donor polyester containing multiple S-nitrosothiol (S-NO) groups covalently attached to the polymer backbone was synthesized through the esterification of poly(ethylene glycol) with mercaptosuccinic acid, followed by the nitrosation of the ,SH moieties. The polynitrosated polyester (PNPE) obtained was blended with poly(methyl methacrylate) (PMMA), yielding solid films capable of releasing NO. Scanning electron microscopy analysis showed that acrylic plates and stainless steel intracoronary stents can be coated with continuous and adherent PNPE/PMMA films. After an initial NO burst, these films release NO spontaneously in dry condition or immersed in aqueous solution at constant rates of 1.8 and 180 nmol/g/h, respectively, for more than 24 h at physiological temperature. PNPE/PMMA coated surfaces were shown to inhibit platelet adhesion when in contact with whole blood. These results show that PNPE/PMMA blend can be used for the coating of blood-contacting surfaces, with potential to inhibit thrombosis and restenosis after stenting. [source] Microwave-Assisted Covalent Sidewall Functionalization of Multiwalled Carbon NanotubesCHEMISTRY - A EUROPEAN JOURNAL, Issue 14 2006Junxin Li Dr. Abstract Thermal cycloaddition of 1,3-dipolar azomethine ylides to the sidewalls of multiwalled carbon nanotubes (MWNTs) has been used to prepare MWNTs that contain 2-methylenethiol-4-(4-octadecyloxyphenyl) (4), N -octyl-2-(4-octadecyloxyphenyl) (5) or 2-(4-octadecyloxyphenyl)pyrrolidine (6) units. All these contain the 4-octadecyloxyphenyl substituent that acts as a solubilizing group. Microwave (MiW)-assisted heating was found to be highly efficient for soluble MWNTs, for which the amount of added groups after only 2 h of MiW heating at 200,°C, determined by using thermogravimetric analysis, was found to be in the same range as that obtained after 100,120 h of conventional heating of soluble and insoluble MWNTs. Solubility is a key feature for a successful MiW-heated reaction; MWNTs insoluble in the reaction medium yielded considerably less addends in the MiW-heated reactions than in the conventionally heated reaction. The location and even distribution of the pyrrolidine units over the outermost layer of the MWNTs was verified by transmission electron microscopy analysis of 4 that had been treated with gold nanoparticles and thoroughly washed to remove gold particles adsorbed on nonfunctionalized parts of the MWNTs. [source] | |||||||||||||||||||