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121.
H. Brockerhoff H. M. Wisniewski L. C. Lipton D. S. Deshmukh 《Neurochemical research》1980,5(6):617-628
We describe an attempt to incorporate a metabolically inert phospholipid analog into animal membranes, especially myelin, in vivo, with the view of eventual long-term membrane modification or membrane engineering. A sonicated suspension of a mixture of [14C] phosphatidylcholine and its dialkyl analog, [3H] tetradecyloctadecano(1)phosphocholine, was injected into the brain of weanling rats. Samples were counted of whole brain, myelin, liver, and carcass, at intervals from 1 to 63 days, and the composition of the extracted labeled lipid was determined by thin-layer chromatography. Both lipid labels were found to be cleared from the body at similar rates, but while phosphatidylcholine was metabolized within a day, with the label appearing mainly in the phosphatidylethanolamine fraction and in nonpolar lipids, the dialkylphosphatidylcholine remained intact, with retention in myelin of a small but almost constant amount for a month. Ways will have to be found to enhance uptake of the lipids by the brain. 相似文献
122.
123.
Sanja Perovic Jürgen Seack Vera Gamulin Werner EG Müller Heinz C Schröder 《BMC cell biology》2001,2(1):7-9
Background
Ethylene is a widely distributed alkene product which is formed enzymatically (e.g., in plants) or by photochemical reactions (e.g., in the upper oceanic layers from dissolved organic carbon). This gaseous compound was recently found to induce in cells from the marine sponge Suberites domuncula, an increase in intracellular Ca2+ level ([Ca2+]i) and an upregulation of the expression of two genes, the potential ethylene-responsive gene, SDERR, and a Ca2+/calmodulin-dependent protein kinase. 相似文献124.
Myelin basic protein and phosphatidylinositol-4-phosphate are phosphorylated in vitro by ATP and solubilized rat brain myelin. When both substrates are present together, the rate of phosphorylation of each is increased about eight-fold. It appears likely that the phosphate turnover of myelin basic protein and of phosphatidylinositol-4-phosphate are coupled in vivo. 相似文献
125.
Amyloid beta-protein (A beta), the major protein of cerebrovascular and plaque amyloid in Alzheimer disease, is considered a primary factor in the pathology of this disease. The effect of synthetic A beta (1-40) on the activity of protein kinase C (PKC) was studied with histones for a substrate in a mixed micellar assay, and with calmodulin-depleted soluble brain proteins in a liposomal system. We report here that A beta affects PKC activity in a biphasic manner. An initial stimulation of PKC was noted at low concentrations of A beta (less than 2.5 microM); while PKC-inhibition was observed in a concentration-dependent manner at higher concentrations of A beta. The in vitro phosphorylation of 20, 47, and 87 kDa brain proteins (known PKC substrates) was significantly reduced by 60 microM A beta. The role of 20 kDa in memory storage, of 87 kDa in neurotransmission and neurosecretory processes, and of 47 kDa in long-term potentiation or memory is well recognized, and A beta is known to have both neurotrophic and neurotoxic effects. Since PKC plays an important role in neuronal function, it is suggested that dual modulation of PKC by A beta may be linked to its neurotrophic and neurotoxic effects. We propose that at low concentrations A beta, by stimulating PKC, may contribute to neurites generation; and at higher concentrations A beta, by inhibiting PKC activity, might lead first to memory impairment, and then to neuronal loss. 相似文献
126.
Stereospecific analyses of several vegetable fats 总被引:11,自引:0,他引:11
The distribution of fatty acids among the positions 1, 2, and 3 of triglycerides of seven vegetable fats has been determined. The fatty acid compositions in positions 1 and 3 are very similar in most cases, but in none of the fats is the distribution completely symmetrical. 相似文献
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128.
Ian R. McFadden Agnieszka Sendek Morgane Brosse Peter M. Bach Marco Baity-Jesi Janine Bolliger Kurt Bollmann Eckehard G. Brockerhoff Giulia Donati Friederike Gebert Shyamolina Ghosh Hsi-Cheng Ho Imran Khaliq J. Jelle Lever Ivana Logar Helen Moor Daniel Odermatt Loïc Pellissier Luiz Jardim de Queiroz Christian Rixen Nele Schuwirth J. Ryan Shipley Cornelia W. Twining Yann Vitasse Christoph Vorburger Mark K. L. Wong Niklaus E. Zimmermann Ole Seehausen Martin M. Gossner Blake Matthews Catherine H. Graham Florian Altermatt Anita Narwani 《Ecology letters》2023,26(2):203-218
Human impacts such as habitat loss, climate change and biological invasions are radically altering biodiversity, with greater effects projected into the future. Evidence suggests human impacts may differ substantially between terrestrial and freshwater ecosystems, but the reasons for these differences are poorly understood. We propose an integrative approach to explain these differences by linking impacts to four fundamental processes that structure communities: dispersal, speciation, species-level selection and ecological drift. Our goal is to provide process-based insights into why human impacts, and responses to impacts, may differ across ecosystem types using a mechanistic, eco-evolutionary comparative framework. To enable these insights, we review and synthesise (i) how the four processes influence diversity and dynamics in terrestrial versus freshwater communities, specifically whether the relative importance of each process differs among ecosystems, and (ii) the pathways by which human impacts can produce divergent responses across ecosystems, due to differences in the strength of processes among ecosystems we identify. Finally, we highlight research gaps and next steps, and discuss how this approach can provide new insights for conservation. By focusing on the processes that shape diversity in communities, we aim to mechanistically link human impacts to ongoing and future changes in ecosystems. 相似文献