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31.
Erwin Scharrer Esther Senn Siegfried Wolffram 《Biological trace element research》1992,33(1-3):109-120
The influence of several thiols (conc. 1 mmol/L) on mucosal uptake of75Se from75Se-labeled selenite (conc. 10 μmol/L) across the brush border of rat jejunum and cecum was investigated in vitro using a short-term
uptake technique.l-Cysteine (l-Cys) stimulated75Se uptake in the mid- and distal jejunum and cecum, but not in the proximal jejunum. The effect was maximal in the distal
jejunum.d-Cys was less effective in the jejunum and similarly effective in the cecum.l-Leucine (l-Leu) andl-glutamic acid significantly reduced the stimulatory effect ofl-Cys on Se uptake in the distal jejunum, whereas the respective effect ofd-Cys was not diminished byl-Leu. Cysteamine stimulated mucosal75Se uptake at all intestinal sites tested, whereas the effect of mercaptopyruvate was restricted to the distal jejunum. Thioglycolate
also enhanced75Se uptake in the distal jejunum. The stimulatory effects ofl-Cys, mercaptopyruvate, and thiologlycolate were Na+-dependent, whereas the effect of cysteamine also occurred in the absence of Na+. Mercaptosuccinate,d-penicillamine, ergothioneine, and thiosulfate did not enhance mucosa75Se uptake. It is concluded from these findings that the reaction of some thiols with selenite results in Se compounds that
are rapidly absorbed by the intestinal epithelium through various Na+-dependent and Na+-independent, mechanisms. The high bioavailability of Se from selenite found by others might thus be the result of the presence
of thiols in the gastrointestinal tract. 相似文献
32.
Sanaa Hamdy Omar Siegfried Honecker Hans-Jürgen Rehm 《Applied microbiology and biotechnology》1992,36(4):518-524
Summary The formation of citric acid, oxalic acid, erythritol and glycerol by three strains of Aspergillus niger immobilized in calcium alginate was investigated and compared with that of free cells when cultivated in shake flasks under phosphate limitation. Morphological changes were followed using an electron microscope. The production of acids and polyols, the consumption of glucose and fructose, and also the morphological changes were strain-dependent. The results also reflected the influence of long storage of a strain on productivity, morphological behaviour and phosphate consumption.
Offprint requests to: H.-J. Rehm 相似文献
33.
Gerry T. Snoek Cees H. Koster Siegfried W. de Laat Martin Heideveld Antony J. Durston Everardus J. J. van Zoelen 《Experimental cell research》1990,187(2)
The Xenopus laevis XTC cell line has been analyzed for the production of polypeptide growth factors and mesoderm-inducing activity. By the use of specific biological assays, it is shown that XTC cells produce a growth factor functionally related to the platelet-derived growth factor (PDGF) and two transforming growth factor (TGF)β-like activities. Mesoderm-inducing activity, as measured on X. laevis ectodermal explants from stage 10 embryos, was found to coelute on a Bio-Gel P-100 column with one of the TGFβ-like activities at an apparent molecular weight of 6–10 kDa. Analysis of the DNA content from XTC cells by flow cytometry demonstrated that the cell line is heterogeneous and consists of both tetraploid and diploid cells. Cloning of the XTC cells and selecting single-cell colonies on the basis of their ability to grow in soft agar resulted in the isolation of several homogeneous, morphologically different clonal derivatives. Analysis of conditioned medium from these clonal derivatives showed that only one of them, the only diploid line among six investigated, produced a strong heat- and acid-stable mesoderm-inducing activity that induced notochord and muscle formation in stage 10 X. laevis ectodermal expiants. The relation between this activity and a recently described TGFβ-like mesoderm-inducing factor obtained from XTC-conditioned medium will be discussed. In conclusion, a clonal cell line derived from X. laevis XTC cells which provides a good source for further characterization of mesoderm-inducing factors has been established. 相似文献
34.
Summary In South Africa seedlings of the exotic Acacia cyclops grow in clumps. The seedlings occur beneath tall elements, or in bush clumps, of the surrounding indigenous vegetation. The tall shrubs are used as perches by birds, and the pattern of seedling distribution is a result of dispersal of seeds by birds. Germination of A. cyclops seeds was enhanced as a result of passage through the gut of a bird, or by artificial treatments simulating actions taking place in the gut of a bird. We examine properties of the seed, and the funicle which is attractive to birds, in relation to aspects of the life history of A. cyclops and the species' success as an invasive plant in South Africa. 相似文献
35.
Johannes Boonstra Paul T. Van Der Saag Wouter H. Moolenaar Siegfried W. De Laat 《Experimental cell research》1981,131(2):452-455
Nerve growth factor (NGF) induces neuronal differentiation of rat pheochromocytoma cells (PC12). Here we show that NGF causes a stimulation of Na+,K+-pump mediated K+ influx, with a maximum at 30 min after addition of NGF. The stimulation of the Na+,K+-pump is completely blocked by the Na+-flux inhibitor amiloride (0.2 mM) and can be mimicked by the Na+ ionophore monensin. These results suggest that NGF causes a rapid enhancement of Na+ influx leading to an activation of the Na+,K+-pump, a mechanism similar to the action of other growth factors. 相似文献
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Ohne Zusammenfassung 相似文献
39.
Kitashova Anastasia Schneider Katja Fürtauer Lisa Schröder Laura Scheibenbogen Tim Fürtauer Siegfried Nägele Thomas 《Photosynthesis research》2021,147(1):49-60
Photosynthesis Research - Photosynthesis and carbohydrate metabolism of higher plants need to be tightly regulated to prevent tissue damage during environmental changes. The intracellular position... 相似文献
40.
Benjamin Liet Nicolas Nys Geraldine Siegfried 《Biochimica et Biophysica Acta (BBA)/Molecular Cell Research》2021,1868(9):119065
Elabela/toddler is the second endogenous ligand recently identified after Apelin, that binds to the G protein-coupled receptor APJ. Elabela is a 54-amino acid peptide initially identified in fish and human genomes and classified as noncoding. This precursor can be cleaved to shorter sequences (32, 21, and 11 amino acids), which bind and activate APJ, and can be blocked by APJ antagonists. Contrary to Apelin and APJ, widely distributed in organs and tissues, Elabela expression is more restricted, and different studies have revealed the potential role of Elabela in cancers. This review summarizes the current studies focusing on the role of Elabela in different cancers. 相似文献