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101.
Life span extension by targeting a link between metabolism and histone acetylation in Drosophila
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The steady-state kinetics of the butyrylcholinesterase-catalysed hydrolysis of butyrylthiocholine and thiophenyl acetate were shown to deviate from Michaelis–Menten kinetics. The `best' empirical rate law was selected by fitting different rate equations to the experimental data by non-linear regression methods. The results were analysed in view of two alternative interpretations: (1) the reaction is catalysed by a mixture of enzymes, or (2) the activity is due to a single enzyme displaying deviations from Michaelis–Menten kinetics. It was concluded that the second alternative applies, and this conclusion was further supported by experiments involving simultaneous hydrolysis of alternative thiol ester substrates (butyrylthiocholine/thiophenyl acetate) as well as alternative thiol ester and oxygen ester substrates (butyrylthiocholine/phenyl acetate; thiophenyl acetate/butyrylcholine; acetylthiocholine/phenyl acetate). On the basis of the conclusion that a single enzyme is responsible for the activity, a molecular model is proposed. This model involves an acylated enzyme, and implies binding to the enzyme of one acyl group and one ester molecule, but not two ester molecules at the same time. Thus butyrylcholinesterase, which is structurally a tetramer, behaves functionally as a co-operative dimer, an interpretation in accordance with available data from active-site titrations. 相似文献
104.
Studies on Effects of Certain Quinones: II. Photosynthetic Incorporation of CO(2) by Chlorella
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The effects of various quinone herbicides and fungicides on the photosynthetic 14CO2 fixation and the incorporation of 14C among the products of photosynthesis in Chlorella pyrenoidosa was investigated. Addition of 30 μm 2,3-dichloro-1,4-naphthoquinone (dichlone), 2-amino-3-chloro-1,4-naphthoquinone (06K-quinone), or 2,3,5,6-tetrachloro-1,4-benzoquinone (chloranil) inhibited CO2 fixation, whereas 1,4-benzoquinone had no effect. Treatment with 3 μm or higher concentrations of dichlone, 06K-quinone or 1,4-benzoquinone also produced marked changes in the pattern of 14C distribution. A noticeable effect was an increase in the proportion of 14C in sucrose and glycine accompanied by a reduction in 14C lipids and glutamic acid. These changes appear to occur as a result of shifts in the flow of carbon along various biosynthetic pathways of photosynthetic CO2 fixation. It is suggested that inactivation of coenzyme A and shortage of reduced triphosphopyridine nucleotide in the quinone-treated cells inhibited the synthesis of lipids and glutamic acid, thereby diverting more carbon into sucrose and glycine. 相似文献
105.
Effect of Potassium on the Release of [3 H]Noradrenaline from Rabbit and Human Pulmonary Artery 总被引:1,自引:0,他引:1
The release of [3H]noradrenaline ( [3H]NA) from rabbit and human isolated pulmonary artery has been measured. Removal of external potassium ions enhanced both the resting and stimulated release of [3H]NA from the strips. On adding K+ to tissues which had been suspended in K+-free Krebs solution, the release of [3H]NA was reduced in both stimulated and unstimulated tissues. Selective inhibition of presynaptic alpha 2-adrenoceptors by yohimbine significantly potentiated the release of [3H]NA evoked by stimulation in K+-free solution. The presynaptic inhibitory effect of NA was much less pronounced when the release was enhanced by the removal of external K+. Since the activity of NA, K-ATPase may be affected by removing K+ or by adding it to tissue previously kept in K+-free solution, the results may indicate involvement of the sodium pump in NA release. 相似文献
106.
When striving to meet an immense challenge, how can we, as restoration ecologists, flourish? Given the ongoing environmental crisis, it is normal to experience ecological grief and discouragement. This article discusses how insights from the ancient philosophy of Stoicism can help environmental practitioners navigate these troubling times. To overcome ecological grief, ecologists can draw on three tenets from Stoic thought: distinguishing between what we can and cannot control; recognizing our contribution as part of a broader community of environmental managers; and focusing on the intent of our actions. We believe that these ideas can help ecologists shoulder the emotional burden of modern environmental practice and focus on working toward a diverse and resilient biosphere. 相似文献
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Plum L Rother E Münzberg H Wunderlich FT Morgan DA Hampel B Shanabrough M Janoschek R Könner AC Alber J Suzuki A Krone W Horvath TL Rahmouni K Brüning JC 《Cell metabolism》2007,6(6):431-445
The contribution of different leptin-induced signaling pathways in control of energy homeostasis is only partly understood. Here we show that selective Pten ablation in leptin-sensitive neurons (PtenΔObRb) results in enhanced Pi3k activation in these cells and reduces adiposity by increasing energy expenditure. White adipose tissue (WAT) of PtenΔObRb mice shows characteristics of brown adipose tissue (BAT), reflected by increased mitochondrial content and Ucp1 expression resulting from enhanced leptin-stimulated sympathetic nerve activity (SNA) in WAT. In contrast, leptin-deficient ob/ob-PtenΔObRb mice exhibit unaltered body weight and WAT morphology compared to ob/ob mice, pointing to a pivotal role of endogenous leptin in control of WAT transdifferentiation. Leanness of PtenΔObRb mice is accompanied by enhanced sensitivity to insulin in skeletal muscle. These data provide direct genetic evidence that leptin-stimulated Pi3k signaling in the CNS regulates energy expenditure via activation of SNA to perigonadal WAT leading to BAT-like differentiation of WAT. 相似文献
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SciRoKo is a user-friendly software tool for the identification of microsatellites in genomic sequences. The combination of an extremely fast search algorithm with a built-in summary statistic tool makes SciRoKo an excellent tool for full genome analysis. Compared to other already existing tools, SciRoKo also allows the analysis of compound microsatellites. AVAILABILITY: free for use: www.kofler.or.at/Bioinformatics. SUPPLEMENTARY INFORMATION: Supplementary data are available at Bioinformatics online. 相似文献