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  • 1
    Electronic Resource
    Electronic Resource
    Contact allergens, but not irritants, alter receptor-mediated endocytosis by human epidermal Langerhans cells (1999)
    Oxford BSL : Blackwell Science Ltd
    British journal of dermatology 140 (1999), S. 0 
    Details
    ISSN: 1365-2133
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Allergic contact dermatitis is a T-cell-mediated inflammation, induced by contact with sensitizers and occurring through the release of epidermal cytokines and the activation of epidermal Langerhans cells (LCs). The aim of this study was to analyse early events of LC activation induced either by contact allergens or by irritants devoid of any contact allergenic properties, in order to obtain an in vitro method to discriminate between these two groups of molecules. Various contact sensitizers and irritants were studied for their effects on the endocytosis of major histocompatibility complex class II (MHC-II) molecules by freshly-isolated human epidermal LCs. As observed by flow cytometry, a spontaneous decrease in the surface expression of MHC-II (HLA-DR) molecules, linked to spontaneous internalization of the MHC-II molecules by LCs, was obtained by moving freshly-isolated LCs from 4 °C to 37 °C. Pre-incubation of LCs with either sensitizers or irritants increased the spontaneous internalization of HLA-DR molecules with a similar magnitude, but no clear discrimination between sensitizer and irritant effects was obtained by flow cytometry analysis. In contrast, confocal microscopy enabled discrimination between the effects of sensitizers and irritants: sensitizer-treated samples showed internalized HLA-DR molecules aggregated in large vesicles with very bright fluorescence; irritant-treated samples were not different from untreated controls and showed compact HLA-DR molecules in small vesicles with diffuse fluorescence, and mostly localized in the submembranous zone. Electron microscopy demonstrated that sensitizer-treated LCs internalized HLA-DR molecules preferentially in lysosomes collected near the nucleus, whereas the irritant-treated and non-treated LCs internalized these molecules in the prelysosomes only near the cell membrane. We conclude that contact allergens and irritants induce distinct patterns of HLA-DR endocytosis, which may be useful for the development of in vitro screening tests.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2133.1999.02650.x
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  • 2
    Electronic Resource
    Electronic Resource
    Growth of aluminum nitride on (111) silicon: Microstructure and interface structure (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 2003-2009 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The growth of hexagonal aluminum nitride directly on (111) silicon has been studied by grazing incidence x-ray diffraction and high resolution electron microscopy as a function of film thickness. Two epitaxial relationships were observed: (1) AlN (0001) [2110]//Si(111) [022¯], which prevails at deposition temperatures larger than 650 °C, and (2) AlN (0001) [101¯0]//Si(111) [022¯]. For a 40 Å thick layer, the average in-plane crystallite size is 162 Å, the in-plane rotation is ∼2° and the dislocations induce an average strain distribution of 0.8%. The Si/AlN interface is very sharp and complete relaxation (down to ∼0.2%) occurs within one bilayer. No long range order was observed at the interface. This implies a low mobility of the AlN species on Si, inhibiting any structural rearrangement. In particular the in-plane rotations originate from the early stage of the layer growth and decrease with the layer thickness, especially for thicknesses larger than 250 Å. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.366929
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  • 3
    Electronic Resource
    Electronic Resource
    Growth, annealing and oxidation of the Ni/MgO (001) interface studied by grazing incidence x-ray scattering (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 84 (1998), S. 4259-4267 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report an in situ grazing incidence x-ray scattering study of the Ni/MgO (001) interface during its formation at room temperature. In-plane measurements reveal that the interface is sharp and that the epitaxial relationship is complex. In the early stages of growth, up to one monolayer of "on site" Ni, in-plane strained to the lattice parameter of MgO, is observed. An oxygen epitaxial site is found. For the on-site fraction the interfacial and Ni interlayer distances were determined. For coverages larger than one monolayer two distinct lattices exist: expanded Ni (001) and Ni (110). The latter exhibits several orientations with respect to the substrate depending on the thickness. The Ni (110) orientations disappear by annealing at high temperature, leaving only the Ni cube/cube orientation. The layer was also almost fully transformed into NiO (001) by high temperature oxidation. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.368643
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  • 4
    Electronic Resource
    Electronic Resource
    The role of bulk H and C species in the chain lengthening of Fischer-Tropsch synthesis over nickel (1997)
    Springer
    Catalysis letters 45 (1997), S. 221-226 
    Details
    ISSN: 1572-879X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract This work documents the possible role of bulk species (dissolved H and C atoms) in the Fischer-Tropsch reaction. This has led us to study the sorption (adsorption or absorption) of hydrogen when increasing the pressure from 0.1 to 5 MPa, the selectivity toward C2+ hydrocarbons in carbon monoxide hydrogenation at 5 MPa total pressure, and the amount of nickel carbide formed in the course of the reaction over unsupported nickel, Ni/SiO2, Ni/TiO2 and Ni/Cr2O3 catalysts. Increasing the hydrogen pressure results in a subsequent sorption which is found to be proportional to the nickel dispersion, and can be attributed either to a completion of the surface hydrogen adlayer (8%) or to a formation of a hydrogen sublayer. No relationship could be found between the selectivity towards C2+ hydrocarbons and the quantity of sorbed hydrogen. A correlation between this selectivity and the amount of nickel carbide formation was demonstrated, suggesting that the active phase which leads to C2+ hydrocarbons is nickel carbide, or that carbon atoms of subsurface sites participate in the homologation reaction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019071713602
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  • 5
    Electronic Resource
    Electronic Resource
    Selective synthesis of alcohols from syngas and hydroformylation of ethylene over supported cluster-derived cobalt catalysts (1996)
    Springer
    Catalysis letters 42 (1996), S. 87-91 
    Details
    ISSN: 1572-879X
    Keywords: higher alcohol synthesis ; vapor phase hydroformylation ; supported cluster-derived cobalt catalysts
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Hydroformylation of ethylene and CO hydrogenation were studied over cobalt-based catalysts derived from reaction of Co2(CO)8 with ZnO, MgO and La2O3 supports. At 433 K a similar activity sequence was reached for both reactions: Co/ ZnO 〉 Co/La2O3 〉 Co/MgO. This confirms the deep analogy between hydroformylation and CO hydrogenation into alcohols. In the CO hydrogenation the selectivity towards alcohol mixture (C1-C3) was found to be near 100% at 433 K for a conversion of 6% over the Co/ZnO catalyst; this catalyst showed oxo selectivity higher than 98% in the hydroformylation of ethylene. Magnetic experiments showed that no metallic cobalt particles were formed at 433 K. It is suggested that the active site for the step that is common to both reactions is related to the surface homonuclear Co2+/[Co(CO)4]− ion-pairing species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00814471
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  • 6
    Electronic Resource
    Electronic Resource
    Effect of ovariectomy on intraosseous vascularization and bone remodelling in rats: Action of tiludronate (1996)
    Springer
    Osteoporosis international 6 (1996), S. 127-129 
    Details
    ISSN: 1433-2965
    Keywords: Bone remodelling ; Ovariectomy ; Rats ; Tiludronate ; Vascularization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In order to study the action of tiludronate on the changes in intraosseous vascularization induced by ovariectomy, and to link these effects to those observed in bone remodelling, 30 female Sprague-Dawley rats (age 40 weeks) were studied. Ten rats were sham-operated and treated by vehicle, 10 rats were ovariec-tomized and treated by vehicle, and 10 rats were ovariectomized and treated orally with tiludronate, 0.16 mmol/kg/per day, 3 days a week for 16 weeks, from the day following ovariectomy. The rats were killed after 4 months, and a histomorphometric study and quantification of intraosseous vessels carried out on the sixth lumbar vertebra. The area of the intraosseous sinusoidal capillaries increased after ovariectomy, which also induced a moderate increase in resorption surfaces and osteoid surfaces leading to a decrease of 40% in the trabecular bone volume at the lumbar spine level. This bone mineral loss was completely prevented by tiludronate, which normalized the bone turnover. However, tiludronate was without any effect on intraosseous vascularization. These results indicate that the surface area of the intraosseous sinusoidal capillaries was correlated positively with resorption surfaces and negatively with trabecular bone volume and the number of bone trabeculae. In these experimental conditions, an inhibitor of bone resorption can exert its positive effect on bone mass without normalization of vascularization.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01623935
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  • 7
    Electronic Resource
    Electronic Resource
    Feasibility of a recombinant human apolipoprotein E reference material (1998)
    Springer
    Fresenius' journal of analytical chemistry 360 (1998), S. 501-504 
    Details
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The aim of this work was to prepare a recombinant apo E material and to determine its suitability as a reference material. We produced human apo E3 using recombinant DNA technology. The cDNA of human apo E3 was cloned in the pARHS bacterial expression vector and used to transfect E. Coli BL21 (DE3) cells. The recombinant protein was then purified in one step by affinity chromatography on a Ni-chelated agarose column under denaturing conditions. The purity of the protein estimated by SDS PAGE was greater than 96%. The physicochemical properties and biological and immunological reactivity of the purified recombinant apo E3 were shown to be close to those of the protein purified from human plasma VLDL. A limited batch of lyophilized apo E material was then prepared. The stability of the lyophilized apo E material examined by temperature accelerated degradation was acceptable. No degradation of the measured apo E was observed after storage of the lyophilized material at +4° C and –20° C for 11 months. The reconstituted lyophilized material, in comparison with human fresh serum samples and with apo E purified from human VLDL, showed no major alteration of its immunological reactivity when assayed by immunoturbidimetry or ELISA.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002160050749
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  • 8
    Electronic Resource
    Electronic Resource
    The visualization and evaluation of bone architecture in the rat using three-dimensional X-Ray microcomputed tomography (1999)
    Springer
    Journal of bone and mineral metabolism 17 (1999), S. 37-44 
    Details
    ISSN: 1435-5604
    Keywords: Key words: bone ; rat ; 3-D X-ray microcomputed tomography ; histomorphometry ; bisphosphonate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract: Microcomputed tomography allows the true three-dimensional structure of bone to be assessed by a nondestructive analysis. This article describes how this technique has for the first time been applied to rat bone to determine the effects of aging, ovariectomy, and antiresorptive drugs on bone structure and how these results compare with those determined by histological and histomorphometric techniques. During the procedure, a micro X-ray source is directed toward the bone sample. Modifications in the X-ray beam induced by bone crystals are determined for a range of acquisitions before three-dimensional reconstruction of bone architecture is performed. Morphometric parameters determined were trabecular bone volume/tissue volume, trabecular number, and trabecular thickness. The results show that ovariectomy has a dramatic effect on rat bone structure. Following treatment with the bone resorption inhibitor tiludronate, the morphometric parameters were significantly improved. The results obtained with three-dimensional microcomputed tomography were in agreement with observations made using classical techniques. Microcomputed tomography should prove useful for evaluating the antiresorptive effects of bisphosphon-ates on bone architecture and in allowing between-drug comparisons.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s007740050061
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