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排序方式: 共有10000条查询结果,搜索用时 31 毫秒
931.
Jochen Schulze Sebastian Seitz Hiroaki Saito Michael Schneebauer Robert P. Marshall Anke Baranowsky Bjoern Busse Arndt F. Schilling Felix W. Friedrich Joachim Albers Alexander S. Spiro Jozef Zustin Thomas Streichert Kristina Ellwanger Christof Niehrs Michael Amling Roland Baron Thorsten Schinke 《PloS one》2010,5(4)
Wnt signalling is a key pathway controlling bone formation in mice and humans. One of the regulators of this pathway is Dkk1, which antagonizes Wnt signalling through the formation of a ternary complex with the transmembrane receptors Krm1/2 and Lrp5/6, thereby blocking the induction of Wnt signalling by the latter ones. Here we show that Kremen-2 (Krm2) is predominantly expressed in bone, and that its osteoblast-specific over-expression in transgenic mice (Col1a1-Krm2) results in severe osteoporosis. Histomorphometric analysis revealed that osteoblast maturation and bone formation are disturbed in Col1a1-Krm2 mice, whereas bone resorption is increased. In line with these findings, primary osteoblasts derived from Col1a1-Krm2 mice display a cell-autonomous differentiation defect, impaired canonical Wnt signalling and decreased production of the osteoclast inhibitory factor Opg. To determine whether the observed effects of Krm2 on bone remodeling are physiologically relevant, we analyzed the skeletal phenotype of 24 weeks old Krm2-deficient mice and observed high bone mass caused by a more than three-fold increase in bone formation. Taken together, these data identify Krm2 as a regulator of bone remodeling and raise the possibility that antagonizing KRM2 might prove beneficial in patients with bone loss disorders. 相似文献
932.
933.
934.
935.
Activity of neck-muscle motoneurones during eye cleaning behaviour in the cricket Gryllus campestris
The activity of neck-muscle motoneurones which control head movements during eye cleaning behaviour was recorded from motor nerves with chronically implanted electrodes in unrestrained crickets. We show that motoneurones of the dorso-ventral muscles displayed strong activity differences between both sides of the neck, with higher discharge frequencies either ipsi- or contralateral to the direction of the head movement. Motoneurones innervating dorsal-longitudinal muscles were equally active on both sides. A single excitatory motoneurone of one dorso-ventral muscle showed a discharge pattern unequivocally related to eye cleaning. Lesions of connectives revealed that this motoneurone is monitored by interneuronal pathways from the suboesophageal ganglion although the primary sensory axons eliciting eye cleaning, project into the prothoracic ganglion. 相似文献
936.
937.
"Wunder" F-BAR domains: going from pits to vesicles 总被引:1,自引:0,他引:1
Clathrin-mediated endocytosis is a key mechanism by which cells take up extracellular cargo. In this issue, Shimada et al. (2007) reveal the mode of action of the F-BAR domain, which deepens the initial membrane pit that forms during clathrin-mediated endocytosis. 相似文献
938.
Triatoma juazeirensis, a new triatomine species from the state of Bahia, Northeastern Brazil, is described. The new species is found among rocks in sylvatic environment and in the peridomicile. Type specimens were deposited in the Entomological Collection of Oswaldo Cruz Institute-Fiocruz, Museum of Zoology of University of S?o Paulo, and Florida Museum of Natural History. T. juazeirensis can be distinguished from the other members of the T. brasiliensis species complex mainly by the overall color of the pronotum, which is dark, and by the entirely dark femora. 相似文献
939.
Gabriel FL Cyris M Jonkers N Giger W Guenther K Kohler HP 《Applied and environmental microbiology》2007,73(10):3320-3326
Recently we showed that degradation of several nonylphenol isomers with alpha-quaternary carbon atoms is initiated by ipso-hydroxylation in Sphingobium xenophagum Bayram (F. L. P. Gabriel, A. Heidlberger, D. Rentsch, W. Giger, K. Guenther, and H.-P. E. Kohler, J. Biol. Chem. 280:15526-15533, 2005). Here, we demonstrate with 18O-labeling experiments that the ipso-hydroxy group was derived from molecular oxygen and that, in the major pathway for cleavage of the alkyl moiety, the resulting nonanol metabolite contained an oxygen atom originating from water and not from the ipso-hydroxy group, as was previously assumed. Our results clearly show that the alkyl cation derived from the alpha-quaternary nonylphenol 4-(1-ethyl-1,4-dimethyl-pentyl)-phenol through ipso-hydroxylation and subsequent dissociation of the 4-alkyl-4-hydroxy-cyclohexadienone intermediate preferentially combines with a molecule of water to yield the corresponding alcohol and hydroquinone. However, the metabolism of certain alpha,alpha-dimethyl-substituted nonylphenols appears to also involve a reaction of the cation with the ipso-hydroxy group to form the corresponding 4-alkoxyphenols. Growth, oxygen uptake, and 18O-labeling experiments clearly indicate that strain Bayram metabolized 4-t-butoxyphenol by ipso-hydroxylation to a hemiketal followed by spontaneous dissociation to the corresponding alcohol and p-quinone. Hydroquinone effected high oxygen uptake in assays with induced resting cells as well as in assays with cell extracts. This further corroborates the role of hydroquinone as the ring cleavage intermediate during degradation of 4-nonylphenols and 4-alkoxyphenols. 相似文献
940.
Peter J. Fashing Felix Mulindahabi Jean-Baptiste Gakima Michel Masozera Ian Mununura Andrew J. Plumptre Nga Nguyen 《International journal of primatology》2007,28(3):529-550
With group sizes sometimes >300 individuals, the Angolan black-and-white colobus (Colobus angolensis ruwenzorii) population
in Nyungwe Forest, Rwanda is an intriguing exception to the tendency for folivores to live in smaller groups than expected
relative to body size. Researchers have hypothesized that the unusually high quality of foliage at Nyungwe allows colobus
there to avoid intragroup feeding competition, releasing constraints on the formation of large groups (Fimbel et al., 2001). We collected data on the activity and ranging patterns of a >300-member Nyungwe colobus group and compared our results
to those from smaller groups in other black-and-white colobus (Colobus spp.) populations. Colobus at Nyungwe spent far more
time feeding and moving (62%) and far less time resting (32%) than black-and-white colobus at any other site. The annual home
range of the Nyungwe colobus was also many times larger (95% minimum convex polygon: 20.7 km
2
; 95% fixed kernel: 24.4 km
2
) than those for other populations. We terminated our research after the group engaged in an unprecedented migration among
black-and-white colobus by moving 13 km south of their former range. Our results suggest that intragroup scramble competition
may be more intense than originally believed within the large colobus groups at Nyungwe and that long periods of resource
renewal may be necessary after a large colobus group passes through an area, thereby potentially helping to explain their
wide ranging patterns. We discuss the socioecological convergence between the Nyungwe colobus and Chinese snub-nosed monkeys
(Rhinopithecus spp.) and suggest directions for future research on the unique black-and-white colobus population at Nyungwe.
相似文献
Peter J. FashingEmail: |