| 461. |
- Schrick, K., et al.
(författare)
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FACKEL is a sterol C-14 reductase required for organized cell division and expansion in Arabidopsis embryogenesis
- 2000
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Ingår i: Genes & Development. - 0890-9369 .- 1549-5477. ; 14:12, s. 1471-1484
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Tidskriftsartikel (refereegranskat)abstract
- In flowering plants, the developing embryo consists of growing populations of cells whose fates are determined in a position-dependent manner to form the adult organism. Mutations in the FACKEL (FK) gene affect body organization of the Arabidopsis seedling. We report that FK is required for cell division and expansion and is involved in proper organization of the embryo. We isolated FK by positional cloning. Expression analysis in embryos revealed that FK mRNA becomes localized to meristematic zones. FK encodes a predicted integral membrane protein related to the vertebrate lamin B receptor and sterol reductases across species, including yeast sterol C-14 reductase ERG24. We provide functional evidence that FK encodes a sterol C-14 reductase by complementation of erg24. GC/MS analysis confirmed that fk mutations lead to accumulation of intermediates in the biosynthetic pathway preceding the C-14 reductase step. Although fk represents a sterol biosynthetic mutant, the phenotype was not rescued by feeding with brassinosteroids (BRs), the only plant sterol signaling molecules known so far. We propose that synthesis of sterol signals in addition to BRs is important in mediating regulated cell growth and organization during embryonic development. Our results indicate a novel role for sterols in the embryogenesis of plants.
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| 462. |
- Segerman, A, et al.
(författare)
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Adenovirus types 11p and 35p show high binding efficiencies for committed hematopoietic cell lines and are infective to these cell lines.
- 2000
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Ingår i: Journal of Virology. - 0022-538X .- 1098-5514. ; 74:3, s. 1457-67
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Tidskriftsartikel (refereegranskat)abstract
- Hematopoietic cells are attractive targets for gene therapy. However, no satisfactory vectors are currently available. A major problem with the most commonly used adenovirus vectors, based on adenovirus type 2 (Ad2) or Ad5, is their low binding efficiency for hematopoietic cells. In this study we identify two adenovirus serotypes with high affinity for hematopoietic cells. The binding efficiency of prototype serotypes Ad4p, Ad11p, and Ad35p for different committed hematopoietic cell lines representing T cells (Jurkat), B cells (DG75), monocytes (U937-2), myeloblasts (K562), and granulocytes (HL-60) was evaluated and compared to that of Ad5v, the commonly used adenovirus vector, using flow cytometry. In contrast to Ad5v, which bound to less than 10% of the cells in all experiments, Ad11p and Ad35p showed high binding efficiency for all of the different hematopoietic cell lines. Ad4p bound to the lymphocytic cell lines to some extent but less well to the myelomonocytic cell lines. The abilities of the different serotypes to infect, replicate, and form complete infectious particles in the hematopoietic cell lines were also investigated by immunostaining, (35)S labeling of viral proteins, and titrations of cell lysates. Ad11p and Ad35p infected the highest proportion of cells, and Ad11p infected all of the cell lines investigated. The Ad11p hexon was expressed equally well in K562 and A549 cells. Jurkat cells also showed high levels of expression of Ad11p hexons, but the production of infectious particles was low. The binding properties of virions were correlated to their ability to infect and be expressed.
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| 463. |
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| 464. |
- Selling, Anna, et al.
(författare)
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Multicomponent Polyanions, 49 : A Potentiometric and (31P, 51V) NMR Study of the Aqueous Molybdovanadophosphate System
- 2000
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Ingår i: European Journal of Inorganic Chemistry. ; 7, s. 1509-21
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Tidskriftsartikel (refereegranskat)abstract
- The equilibrium speciation of the quaternary system H+/MoO42-/HVO42-/HPO42- in aqueous 0.600 M Na(Cl) at 25 °C and 90 °C was studied by pH potentiometry and 31P (202.5 MHz) and 51V (131.6 MHz) NMR spectrometry. The study focused on solutions containing the oxoanion components in the ratios (Mo + V)/P = 12:1 and Mo/V 3.8, in the pH range 0-5, wherein Keggin anions of the formula [HzMo12-xVxPO40](3+x-z)- with x = 1-3 are the predominant species. Formation constants (log ) and pKa values for Keggin anions with x = 1-3 were determined from 31P and 51V resonance chemical shift data, 31P resonance intensity data, and pH potentiometric data with the multidata least squares calculation program LAKE. The [Mo11VPO40]4- anion does not protonate, [Mo10V2PO40]5- anions can be monoprotonated, and [Mo9V3PO40]6- anions can be triprotonated. The six most intense 31P NMR resonances of [HzMo9V3PO40](6 - z)- could be followed over the pH range studied. It was also possible to assign some 31P resonances to a specific isomer of [Mo9V3PO40]6-.
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| 465. |
- Servin, Martin, et al.
(författare)
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Parametric excitation of Alfvén waves by gravitational radiation
- 2000
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Ingår i: Physical review. E. - : American Physical Society. - 2470-0045 .- 2470-0053. ; 62, s. 8493-8500
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Tidskriftsartikel (refereegranskat)abstract
- We consider the parametric excitation of Alfvén waves by gravitational radiation propagating on a Minkowski background, parallel to an external magnetic field. As a starting point, standard ideal magnetohydrodynamics equations incorporating the curvature of space-time has been derived. The growth rate of the Alfvén waves has been calculated, using the normal-mode approach. Various astrophysical applications of our investigations are discussed, and finally we demonstrate that the coupling coefficients of the interacting modes fulfill the Manley-Rowe relations.
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| 466. |
- Shelankov, Andrei, et al.
(författare)
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Quasiclassical theory of superconductivity : A multiple-interface geometry
- 2000
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 61:10, s. 7077-7100
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Tidskriftsartikel (refereegranskat)abstract
- A method is suggested that allows one to study multiple coherent reflection/transmissions by partially transparent interfaces (e.g., in multilayer mesoscopic structures or grain boundaries in high T-c's), in the framework of the quasiclassical theory of superconductivity. It is argued that in the presence of interfaces, a straight-line trajectory transforms to a simple connected one-dimensional tree (graph) with knots, i.e., the points where the interface scattering events occur and pieces of the trajectories are coupled. For the two-component trajectory "wave function" which factorizes the Gor'kov matrix Green's function, a linear boundary condition on the knot is formulated for an arbitrary interface, specular or diffusive (in the many channel model). From the new boundary condition, we derive (i) the excitation scattering amplitude for the multichannel Andreev/ordinary reflection/transmission processes; (ii) the boundary conditions for the Riccati equation; (iii) the transfer matrix which couples the trajectory Green's function before and after the interface scattering. To show the usage of the method, the cases of a him separated from a hulk superconductor by a partially transparent interface, and a SIS' sandwich with finite thickness layers, are considered. The electric current response to the vector potential (the superfluid density rho(s)) with the pi phase difference in S and S' is calculated for the sandwich. It is shown that the model is very sensitive to imperfection of the SS' interface: the low temperature response being paramagnetic (rho(s) < 0) in the ideal system case, changes its sign and becomes diamagnetic (rho(s) > 0) when the probability of reflection is as low as a few percent.
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| 467. |
- Silverman, N, et al.
(författare)
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A Drosophila IkappaB kinase complex required for Relish cleavage and antibacterial immunity.
- 2000
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Ingår i: Genes Dev. - 0890-9369. ; 14:19, s. 2461-71
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Tidskriftsartikel (refereegranskat)abstract
- Here we report the identification of a Drosophila IkappaB kinase complex containing DmIKKbeta and DmIKKgamma, homologs of the human IKKbeta and IKKgamma proteins. We show that this complex is required for the signal-dependent cleavage of Relish, a member of the Rel family of transcriptional activator proteins, and for the activation of antibacterial immune response genes. In addition, we find that the activated DmIKK complex, as well as recombinant DmIKKbeta, can phosphorylate Relish in vitro. Thus, we propose that the Drosophila IkappaB kinase complex functions, at least in part, by inducing the proteolytic cleavage of Relish. The N terminus of Relish then translocates to the nucleus and activates the transcription of antibacterial immune response genes. Remarkably, this Drosophila IkappaB kinase complex is not required for the activation of the Rel proteins Dif and Dorsal through the Toll signaling pathway, which is essential for antifungal immunity and dorsoventral patterning during early development. Thus, a yet to be identified IkappaB kinase complex must be required for Rel protein activation via the Toll signaling pathway.
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| 468. |
- Simpson, Stuart L, et al.
(författare)
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Pyrocatechol Violet Complexation at the Boehmite–Water Interface
- 2000
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Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 0021-9797. ; 229:2, s. 568-74
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Tidskriftsartikel (refereegranskat)abstract
- Acid/base reactions and pyrocatechol violet complexation at the boehmite–solution interface have been investigated in 0.10 M K(Cl) solution at 298.2 K in the range 5.0≤−log h≤9.0. Equilibrium measurements were performed as potentiometric titrations complemented by spectrophotometric analysis of a ligand (batch adsorption experiments). The experimental data were evaluated on the basis of the extended constant capacitance model, allowing for inner-sphere and/or outer-sphere complexation. The acid/base properties are described by the equilibria: H++≡AlOH ≡AlOH2+; log β1,1,0(int)=7.46±0.04 and ≡AlOH ≡AlO−+H+; log β−1,1,0(int)=−9.87±0.12. The specific capacitance was determined as 1.00 F m−2. The binding of pyrocatechol violet {PCV, 2-[(3,4-dihydroxyphenyl)(3-hydroxy-4-oxocyclohexa-2,5-diene-1-ylidene)methyl]benzenesulfonic acid}, H4L, was described by the formation of a single inner-sphere complex according to the reaction ≡AlOH+H4L≡AlL3−+3H++H2O. Allowing for a charge distribution of this complex between the inner plane and β-plane (−2, −1), a significant improvement of the fit was obtained. The adsorbed complex exhibited a dark blue color over the pH range 5–8.5, indicative of proton loss from the 1,2-dihydroxyl moiety. Furthermore, DRIFT spectra showed the bonding environment of PCV bound to the surface to exhibit similarities with corresponding catechol adsorption to different aluminium (hydr)oxides. These spectral features turned out to be very similar to soluble catechol complexes of Al(III). Thus, it is suggested that PCV forms a mononuclear chelating complex at the boehmite–water interface. The maximum surface coverage reached was ca. 33%, indicating that the high negative charge of the species may result in surface charge “saturation” rather than saturation of surface binding sites. Steric hindrances caused by the large size of PCV may also contribute to the low surface coverage.
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| 469. |
- Sironen, Reijo, et al.
(författare)
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Transcriptional activation in chondrocytes submitted to hydrostatic pressure.
- 2000
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Ingår i: Biorheology. - : IOS Press. - 0006-355X .- 1878-5034. ; 37:1-2, s. 85-93
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Tidskriftsartikel (refereegranskat)abstract
- At present, only a little is known about the transcriptional regulation in chondrocytes submitted to various physicomechanical factors known to exist in articular cartilage. Recently, we have investigated the effects of hydrostatic pressure on transcriptional control in chondrocytes using human chondrosarcoma and immortalized chondrocyte cell lines for the experiments. Hydrostatic pressure was applied on the cells in a special computer-controlled, water-filled pressure chamber, where cyclic and static pressures up to 32 MPa can be created. Differential display RT-PCR and probing of cDNA arrays are the methods we have used to study differential gene expression due to hydrostatic pressure. By differential display RT-PCR experiments, we have observed several differentially expressed cDNA bands under continuous 30 MPa hydrostatic pressure, while 30 MPa cyclic pressure at 1 Hz produced much fewer changes. In the first phase of our studies, we have focused on the effects of 30 MPa hydrostatic pressure because it causes a unique hsp70-mediated stress response in immortalized chondrocytes. Differential display RT-PCR screening provided us with several clones that derive from low-abundance mRNAs, such as death-associated protein 3 (DAP3), a nucleotide-binding protein which increases due to interferon-gamma induced cell death; PTZ-17 (or p311), a seizure-related protein; H-NUC, a nuclear DNA binding protein; and one new gene of unknown function. In Northern blots, an induction was confirmed for the new gene, DAP3 and PTZ-17 were down-regulated in some but not in all parallel experiments; however, basal level of H-NUC mRNA was too low to be detected in Northern blots. We then chose to widen our screening to a number of known genes arrayed as cDNA blots. Under 30 MPa continuous hydrostatic pressure, four different time points were chosen (0, 3, 6 and 24 h) for the experiments. The screening of 588 cDNAs showed 15 up-regulated and 6 down-regulated genes. Consistently with our previous results hsp70 was highly induced, as well as hsp40, a chaperone protein functioning together with hsp70. Gadd45 and to a lesser extent Gadd153 (stress genes induced by, e.g., ionizing radiation and ischaemia) were up-regulated, as well as p21waf1,cip1, a protein participating in cell cycle regulation that can interact with Gadd45. Northern blots confirmed Gadd45 induction. Down-regulated transcripts included, e.g., DAD-1, glutathione S-transferase pI, DNA-binding inhibitor ID-1H, and cytoplasmic dynein light chain.
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| 470. |
- Sjöberg, R L
(författare)
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The catechism effect : child testimonies during a 17th-century witch panic as related to educational achievement.
- 2000
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Ingår i: Memory. - : Informa UK Limited. - 0965-8211 .- 1464-0686. ; 8:2
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Tidskriftsartikel (refereegranskat)abstract
- Testimonies from 488 children given to the priests of the parish of Rättvik during a preliminary investigation of a Swedish witch panic in 1670-71 are examined in relation to records from parish catechetical meetings held in 1671. The result implies that children who knew and understood at least parts of Luther's catechism were less liable to have falsely alleged that they had been kidnapped by female satanists during the witch panic of the previous year. It is suggested that these effects were caused by differences in cognitive, social, and emotional resources among these children as compared to those who were unable to learn and understand any parts of Luther's catechism.
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