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81.
To verify the presence of glycolaldehyde in wine resulting from reduction of glyoxal after malolactic fermentation, sterilized solutions of synthetic cultures were inoculated with a lactic bacterium of the type Oenococcus oeni. Fermentation was also carried out on solutions with glyoxal added. The resulting glycolaldehyde concentrations turned out to be associated with the amounts of glyoxal present, and glyoxal was seen to decrease as glycolaldehyde increased. In addition, it was observed that glyoxal principally forms from breakdown of sugars and that reduction to glycolaldehyde is mainly promoted by bacterial activity. Finally, the ability of glycolaldehyde to induce browning of (+)-catechin in a model wine system was verified and turned out to be about 10 times higher than that of ascorbic acid.  相似文献   
82.
During development and tissue homeostasis, cells must integrate different signals. We investigated how cell behavior is controlled by the combined activity of transforming growth factor-beta (TGF-beta) and receptor tyrosine kinase (RTK) signaling, whose integration mechanism is unknown. We find that RTK/Ras/MAPK (mitogen-activated protein kinase) activity induces p53 N-terminal phosphorylation, enabling the interaction of p53 with the TGF-beta-activated Smads. This mechanism confines mesoderm specification in Xenopus embryos and promotes TGF-beta cytostasis in human cells. These data indicate a mechanism to allow extracellular cues to specify the TGF-beta gene-expression program.  相似文献   
83.
Sarcomeric oscillations in frog skeletal muscle fibers   总被引:1,自引:0,他引:1  
Brief asynchronous, small-amplitude, cyclic, longitudinal displacements of the striations of frog skeletal muscle fibers were observed with ordinary light microscopy after application of caffeine and certain quaternary ammonium compounds. With time these oscillations became synchronized and evolved into peristaltic-like movements. The oscillations were influenced by sarcomere length, temperature, external concentration of calcium ions, membrane potential, and disruption of the transverse tubules.  相似文献   
84.
Radar soundings of the subsurface of Mars   总被引:2,自引:0,他引:2  
The martian subsurface has been probed to kilometer depths by the Mars Advanced Radar for Subsurface and Ionospheric Sounding instrument aboard the Mars Express orbiter. Signals penetrate the polar layered deposits, probably imaging the base of the deposits. Data from the northern lowlands of Chryse Planitia have revealed a shallowly buried quasi-circular structure about 250 kilometers in diameter that is interpreted to be an impact basin. In addition, a planar reflector associated with the basin structure may indicate the presence of a low-loss deposit that is more than 1 kilometer thick.  相似文献   
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Globular fossils showing palintomic cell cleavage in the Ediacaran Doushantuo Formation, China, are widely regarded as embryos of early metazoans, although metazoan synapomorphies, tissue differentiation, and associated juveniles or adults are lacking. We demonstrate using synchrotron-based x-ray tomographic microscopy that the fossils have features incompatible with multicellular metazoan embryos. The developmental pattern is comparable with nonmetazoan holozoans, including germination stages that preclude postcleavage embryology characteristic of metazoans. We conclude that these fossils are neither animals nor embryos. They belong outside crown-group Metazoa, within total-group Holozoa (the sister clade to Fungi that includes Metazoa, Choanoflagellata, and Mesomycetozoea) or perhaps on even more distant branches in the eukaryote tree. They represent an evolutionary grade in which palintomic cleavage served the function of producing propagules for dispersion.  相似文献   
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This article examines quantitatively the determinants of purchase decisions based on corporate social responsibility (CSR), adopting a hierarchical conceptual model of decision making where the key factors are personal concern, information availability and financial considerations. We use best–worst methods to assess consumer priorities (personal concern) for CSR activities in milk production; and elicit consumer interpretation of four labels (organic, Validus, Colorado Proud and rBST free) in terms of CSR and other outcomes (information availability). We then elicit willingness to pay (WTP) for the labels (financial considerations), and estimate regression models to determine how predictive each label perceptual profile is of WTP for milk. Animal welfare and sustainable agricultural practices are the most important activities, and milk labels do convey CSR-related messages. With the exception of the pair animal welfare-Validus, the link between CSR messages and WTP is tenuous. The discussion emphasizes the central role of each label’s perceptual profile in triggering product differentiation among consumers.  相似文献   
90.
Addiction profoundly alters motivational circuits so that drugs become powerful reinforcers of behavior. The interoceptive system continuously updates homeostatic and emotional information that are important elements in motivational decisions. We tested the idea that interoceptive information is essential in drug craving and in the behavioral signs of malaise. We inactivated the primary interoceptive cortex in amphetamine-experienced rats, which prevented the urge to seek amphetamine in a place preference task. Interoceptive insula inactivation also blunted the signs of malaise induced by acute lithium administration. Drug-seeking and malaise both induced Fos expression, a marker of neuronal activation, in the insula. We conclude that the insular cortex is a key structure in the perception of bodily needs that provides direction to motivated behaviors.  相似文献   
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