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951.
Preillumination of intact cells of the eukaryotic, halotolerant, cell-wall-less green alga Dunaliella salina induces a dark ATPase activity the magnitude of which is about 3–5-fold higher than the ATPase activity observed in dark-adapted cells. The light-induced activity arises from the activation and stabilization in vivo of chloroplast coupling factor 1 (CF1). This activity, 150–300 μmol ATP hydrolyzed/mg Chl per h, rapidly decays (with a half-time of about 6 min at room temperature) in intact cells but only slowly decays (with a half-time of about 45 min at room temperature) if the cells are lysed by osmotic shock immediately after illumination. The activated form of the ATPase in lysed cells is inhibited if the membranes are treated with ferri- but not ferrocyanide, suggesting that the stabilization of the activated form of CF1 is due to the reduction of the enzyme in vivo in the light. 相似文献
952.
J van der Bosch S Rüller D Horn R Schumann M Schlaak 《Experimental cell research》1990,187(2):185-192
The population development of five human tumor cell lines is examined under the influence of elutriator-prepared human monocytes in a serum-free hormone- and growth factor-supplemented medium. Analysis was performed by electronic counting and sizing of tumor cell nuclei and flow cytometric detection of cell cycle phases. Tumor cell death is triggered at rather low monocyte:tumor cell ratios (1:2 to 1:4) whereas it is strongly reduced at high monocyte densities. Furthermore, it is shown that confluence of the target cell population is a necessary prerequisite for lysis. The data suggest that in monocyte/tumor cell cocultures the decision on target cell lysis is not made by the effector cell, but rather by the target cell and that the criterion for this decision is the target cell's ability or inability to respond to a monocyte challenge by arresting the cell cycle in G1. Interactions between target cells play an important role in determining the result of this decision process. A common basis is suggested for this kind of density-dependent monocyte-triggered lysis and density-dependent cell death in 3T3 cell cultures as described previously. 相似文献
953.
954.
Marcos A. F. Sales Marcel B. Lacerda Bruno L. D. Horn Isabel A. P. de Oliveira Cesar L. Schultz 《PloS one》2016,11(2)
The view of spinosaurs as dinosaurs of semi-aquatic habits and strongly associated with marginal and coastal habitats are deeply rooted in both scientific and popular knowledge, but it was never statistically tested. Inspired by a previous analysis of other dinosaur clades and major paleoenvironmental categories, here we present our own statistical evaluation of the association between coastal and terrestrial paleoenvironments and spinosaurids, along with other two theropod taxa: abelisaurids and carcharodontosaurids. We also included a taphonomic perspective and classified the occurrences in categories related to potential biases in order to better address our interpretations. Our main results can be summarized as follows: 1) the taxon with the largest amount of statistical evidence showing it positively associated to coastal paleoenvironments is Spinosauridae; 2) abelisaurids and carcharodontosaurids had more statistical evidence showing them positively associated with terrestrial paleoenvironments; 3) it is likely that spinosaurids also occupied spatially inland areas in a way somehow comparable at least to carcharodontosaurids; 4) abelisaurids may have been more common than the other two taxa in inland habitats. 相似文献
955.
956.
957.
The Functional Magnetic Resonance Imaging Data Center (fMRIDC): the challenges and rewards of large-scale databasing of neuroimaging studies. 总被引:3,自引:0,他引:3
958.
Domestic dogs are skillful at using the human pointing gesture. In this study we investigated whether dogs take contextual information into account when following pointing gestures, specifically, whether they follow human pointing gestures more readily in the context in which food has been found previously. Also varied was the human''s tone of voice as either imperative or informative. Dogs were more sustained in their searching behavior in the ‘context’ condition as opposed to the ‘no context’ condition, suggesting that they do not simply follow a pointing gesture blindly but use previously acquired contextual information to inform their interpretation of that pointing gesture.Dogs also showed more sustained searching behavior when there was pointing than when there was not, suggesting that they expect to find a referent when they see a human point. Finally, dogs searched more in high-pitched informative trials as opposed to the low-pitched imperative trials, whereas in the latter dogs seemed more inclined to respond by sitting. These findings suggest that a dog''s response to a pointing gesture is flexible and depends on the context as well as the human''s tone of voice. 相似文献
959.
Robert J. Saphirstein Yuan Z. Gao Mikkel H. Jensen Cynthia M. Gallant Susanne Vetterkind Jeffrey R. Moore Kathleen G. Morgan 《PloS one》2013,8(4)
Increased aortic stiffness is an acknowledged predictor and cause of cardiovascular disease. The sources and mechanisms of vascular stiffness are not well understood, although the extracellular matrix (ECM) has been assumed to be a major component. We tested here the hypothesis that the focal adhesions (FAs) connecting the cortical cytoskeleton of vascular smooth muscle cells (VSMCs) to the matrix in the aortic wall are a component of aortic stiffness and that this component is dynamically regulated. First, we examined a model system in which magnetic tweezers could be used to monitor cellular cortical stiffness, serum-starved A7r5 aortic smooth muscle cells. Lysophosphatidic acid (LPA), an activator of myosin that increases cell contractility, increased cortical stiffness. A small molecule inhibitor of Src-dependent FA recycling, PP2, was found to significantly inhibit LPA-induced increases in cortical stiffness, as well as tension-induced increases in FA size. To directly test the applicability of these results to force and stiffness development at the level of vascular tissue, we monitored mouse aorta ring stiffness with small sinusoidal length oscillations during agonist-induced contraction. The alpha-agonist phenylephrine, which also increases myosin activation and contractility, increased tissue stress and stiffness in a PP2- and FAK inhibitor 14-attenuated manner. Subsequent phosphotyrosine screening and follow-up with phosphosite-specific antibodies confirmed that the effects of PP2 and FAK inhibitor 14 in vascular tissue involve FA proteins, including FAK, CAS, and paxillin. Thus, in the present study we identify, for the first time, the FA of the VSMC, in particular the FAK-Src signaling complex, as a significant subcellular regulator of aortic stiffness and stress. 相似文献
960.
Core Hunter: an algorithm for sampling genetic resources based on multiple genetic measures 总被引:1,自引:0,他引:1
Chris Thachuk José Crossa Jorge Franco Susanne Dreisigacker Marilyn Warburton Guy F Davenport 《BMC bioinformatics》2009,10(1):243