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991.
Defective epidermal barrier in neonatal mice lacking the C-terminal region of connexin43 总被引:4,自引:0,他引:4 下载免费PDF全文
Maass K Ghanem A Kim JS Saathoff M Urschel S Kirfel G Grümmer R Kretz M Lewalter T Tiemann K Winterhager E Herzog V Willecke K 《Molecular biology of the cell》2004,15(10):4597-4608
More than 97% of mice in which the C-terminal region of connexin43 (Cx43) was removed (designated as Cx43K258stop) die shortly after birth due to a defect of the epidermal barrier. The abnormal expression of Cx43K258stop protein in the uppermost layers of the epidermis seems to perturb terminal differentiation of keratinocytes. In contrast to Cx43-deficient mice, neonatal Cx43K258stop hearts show no lethal obstruction of the right ventricular outflow tract, but signs of dilatation. Electrocardiographies of neonatal hearts reveal repolarization abnormalities in 20% of homozygous Cx43K258stop animals. The very rare adult Cx43K258stop mice show a compensation of the epidermal barrier defect but persisting impairment of cardiac function in echocardiography. Female Cx43K258stop mice are infertile due to impaired folliculogenesis. Our results indicate that the C-terminally truncated Cx43K258stop mice lack essential functions of Cx43, although the truncated Cx43 protein can form open gap junctional channels. 相似文献
992.
993.
Chandrasekar Rajadurai Karsten Falk Volker Enkelmann Martin Baumgarten 《Inorganica chimica acta》2005,358(12):3391-3397
Two alternating 1-D metal-radical linear [L:Cu(hfac)2]n and zig-zag [L:Mn(hfac)2]n chains (where L = 4-trimethylsilylethynyl-1-(4,4,5,5-tetramethyl-3-oxylimidazoline-1-oxide)benzene) and hfac = hexafluoroacetylacetonate) are described and characterized by X-ray diffraction of their crystals. Bulk magnetic measurements of L:Cu(hfac)2 indicated a ferromagnetic interaction with J = 6 cm−1 and L:Mn(hfac)2 yielded ferrimagnetic interactions with J = −95 cm−1. For the latter, a strong increase of their magnetic moment at lowest temperatures was observed only at very low static magnetic field, while for Hdc > 0.05 T saturation effect led to a downward slope after reaching a maximum. 相似文献
994.
Although size at maturity and size and number of offspring are life-history traits widely studied in sexual and parthenogenetic reproduction, there is no such research on animals reproducing asexually without the involvement of gametes. Here we present an individual-based model in combination with experiments to study the clonal growth of Stylaria lacustris, an oligochaete reproducing through fission. We studied the effect of individual size at fission and fission ratio on clone fitness. Our results show that in benign environments without predators, fitness is higher when small worms produce small offspring. Then we included size-specific sublethal predation and found that the fitness of the clone is maximized when parental worms start fission at a large size and produce large descendants intercalated in the middle of the parental worm's body. These results agree with empirical findings. Furthermore, the results of our own laboratory experiment revealed that when S. lacustris is exposed to chemical alarm signals from injured conspecifics, it alters its life history in the same direction as predicted by the model. Our findings suggest that the effect of size-specific sublethal predation is similar to the effect of size-specific lethal predation because both modes of predation result in size-dependent prey mortality. 相似文献
995.
Schildknecht S Bachschmid M Weber K Maass D Ullrich V 《Biochemical and biophysical research communications》2005,327(1):43-48
Lipopolysaccharide (LPS) exposure to cells and tissues can mimic the biochemical events leading to septic shock. Previous data demonstrated a massive upregulation of prostaglandin endoperoxide H2 synthase (PGHS-2), but not NO synthase-2 (NOS-2) in bovine smooth muscle cells (SMC) between 2 and 12 h of LPS exposure. This caused an abundant release of prostacyclin (PGI2) by constitutive PGI2-synthase as a counterregulation to a dysfunctional endothelium. We here report that human as well as bovine SMC mainly respond by the induction of PGHS-2 and the subsequent release of PGI2, whereas rat SMC exhibited a distinct induction of NOS-2 and released significantly higher amounts of *NO compared with cattle and human. The induction of either PGHS-2 or NOS-2 in the three different species investigated seems to be mutually exclusive in the time window of 2-24 h. This finding should be considered in the setup of experimental models for the investigation of septic shock. 相似文献
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997.
998.
Embolism reversal in rice plants was studied by testing the plant's ability to refill embolized conduits while xylem pressures were substantially negative. Intact, potted plants were water-stressed to a xylem pressure of -1.88 ± 0.1 MPa and a 66.3 ± 3.8% loss of xylem conductivity (PLC) by cavitation. Stressed plants were carefully rewatered, allowing xylem pressure to rise, but not above the theoretical threshold of c. -0.15 MPa for embolism collapse. Despite xylem pressures being more negative than this threshold, the PLC fell significantly (28.5 ± 5.6%), indicating the refilling of vessels. Above c. -1.0 MPa, almost all plants regained their maximum hydraulic conductivity. Dye uptake experiments showed the same pattern of embolism refilling despite negative pressure. Refilling was prevented in plants that were light-starved for 5 d, suggesting the unknown mechanism is dependent on metabolic energy. Results are among the first showing that herbaceous plants can reverse embolism without bulk xylem pressures rising near or above atmospheric. 相似文献
999.
Welbourn S Green R Gamache I Dandache S Lohmann V Bartenschlager R Meerovitch K Pause A 《The Journal of biological chemistry》2005,280(33):29604-29611
The hepatitis C virus NS2/3 protease is responsible for cleavage of the viral polyprotein between nonstructural proteins NS2 and NS3. We show here that mutation of three highly conserved residues in NS2 (His(952), Glu(972), and Cys(993)) abrogates NS2/3 protease activity and that introduction of any of these mutations into subgenomic NS2-5B replicons results in complete inactivation of NS2/3 processing and RNA replication in both stable and transient replication assays. The effect of uncleaved NS2 on the various activities of NS3 was therefore explored. Unprocessed NS2 had no significant effect on the in vitro ATPase and helicase activities of NS3, whereas immunoprecipitation experiments demonstrated a decreased affinity of NS4A for uncleaved NS2/3 as compared with NS3. This subsequently resulted in reduced kinetics in an in vitro NS3 protease assay with the unprocessed NS2/3 protein. Interestingly, NS3 was still capable of efficient processing of the polyprotein expressed from a subgenomic replicon in Huh-7 cells in the presence of uncleaved NS2. Notably, we show that fusion with NS2 leads to the rapid degradation of NS3, whose activity is essential for RNA replication. Finally, we demonstrate that uncleaved NS2/3 degradation can be prevented by the addition of a proteasome inhibitor. We therefore propose that NS2/3 processing is a critical step in the viral life cycle and is required to permit the accumulation of sufficient NS3 for RNA replication to occur. The regulation of NS2/3 cleavage could constitute a novel mechanism of switching between viral RNA replication and other processes of the hepatitis C virus life cycle. 相似文献
1000.
Petrosky KY Ou HD Löhr F Dötsch V Lim WA 《The Journal of biological chemistry》2005,280(46):38528-38536
LIN-2/7 (L27) domains are protein interaction modules that preferentially hetero-oligomerize, a property critical for their function in directing specific assembly of supramolecular signaling complexes at synapses and other polarized cell-cell junctions. We have solved the solution structure of the heterodimer composed of the L27 domains from LIN-2 and LIN-7. Comparison of this structure with other L27 domain structures has allowed us to formulate a general model for why most L27 domains form an obligate heterodimer complex. L27 domains can be divided in two types (A and B), with each heterodimer comprising an A/B pair. We have identified two keystone positions that play a central role in discrimination. The residues at these positions are energetically acceptable in the context of an A/B heterodimer, but would lead to packing defects or electrostatic repulsion in the context of A/A and B/B homodimers. As predicted by the model, mutations of keystone residues stabilize normally strongly disfavored homodimers. Thus, L27 domains are specifically optimized to avoid homodimeric interactions. 相似文献