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924.
Hermann-Josef Egger Josef Reiner Gerhard Spiteller 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》1978,145(3):359-369
Urine steroid profiles of hirsute womenSteroid profiles of women suffering from idiopathic hirsutism show in more than 50% of the cases a 10–100 fold increase in the excretion of dehydroepiandrosterone (DHEA) compared with normal values.The excretion of DHEA was reduced much more than that of other 17-ketosteroids if the adrenals (NNR) were suppressed by dexamethasone (DXM). Within one week they reached values at the compound noise level of the gas chromatograms. If the ovaries were stimulated with human chorionic gonadotropin during continued suppression of the NNR with DXM no increase of DHEA could be detected. 相似文献
925.
Gerhard Röbbelen 《Molecular & general genetics : MGG》1962,93(2):256-263
Summary By making a tongue-slit in the shaft of the inflorescence ofArabidopsis thaliana 7 different urethanes (1/200 mol+1/200 mol KCl) were forced into the buds through the transpiration stream. After this treatment with 6 of these substances the frequency of the monohybrid segregating mutations was significantly raised 5- to 10times over the control as determined by seedling tests.The mutation frequency was positively correlated with the size of the urethan molecule and seemed to be little affected by its chemical substitution. The mutants were of the same type than those obtained after irradiation with X-rays.These results are in agreement with the conception that the mutagenic effect of the urethanes is indirect and probably due to general disturbances of different metabolic processes in the cell.
Mit 2 Textabbildungen 相似文献
Mit 2 Textabbildungen 相似文献
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A brush border preparation from rabbit renal tubules containing a high yield of vesicles has been used to study the transfer of d-glucose through the brush border membrane. In the presence of an Na+ gradient across the vesicular membrane, the vesicles could concentrate d-glucose to a factor of 1.5, whereas in the absence of an Na+ gradient, only equilibrium with the medium was achieved. Two types of transfer could be distinguished by their requirement of Na+, their sensitivity to phlorizin and their pH optimum. The Na+-independent transfer was about 100 times less sensitive to phlorizin than the Na+-dependent path and exhibited a pH optimum between 7 and 8, whereas the Na+-dependent transfer was highest at a pH between 8 and 9.The brush border preparation could be freed of most of the contaminating material derived from the basal and lateral tubular cell membrane by a discontinuous density gradient centrifugation. It still showed both forms of transfer to a similar extent, indicating that both are located in the brush border membrane.A study of the sensitivity of d-glucose transfer to phlorizin, in the presence and absence of Na+ at different temperature, suggests a single carrier species functioning in two interchangeable conformational states with different affinities for phlorizin rather than two transfer systems working independently. 相似文献
929.
Priv.-Doz. Dr. Brita von Gaudecker Gerhard G. Steinmann Martin Leo Hansmann Joachim Harpprecht Novica M. Milicevic Hans Konrad Müller-Hermelink 《Cell and tissue research》1986,244(2):403-412
Summary The epithelial framework of the human thymus has been studied in parallel by immunohistochemical methods at the light- and electron-microscopic levels. Different monoclonal antibodies were used, reacting with components of the major histocompatibility complex, keratins, thymic hormones and other as yet antigenically undefined substances, which show specific immunoreactivities with human thymus epithelial cells.The electron-microscopic immunocytochemical observations clearly confirm microtopographical differences of epithelial cells not only between the thymic cortex and medulla, but also within the cortex itself. At least four subtypes of epithelial cells could be distinguished: 1) the cortical surface epithelium; 2) the main cortical epithelial cells and thymic nurse cells; 3) the medullary epithelial cells; and 4) the epithelial cells of Hassall's corpuscles.The various epithelial cell types of the thymus display several common features like tonofilaments, desmosomes and some surface antigens as demonstrated by anti-KiM3. In other respects, however, they differ from each other. The cortical subtype of thymic epithelial cells including the thymic nurse cells shows a distinct pattern of surface antigens reacting positively with antibodies against HLA-DR (anti-HLA-DR) and anti-21A62E. Electron-microscopic immunocytochemistry with these antibodies clearly reveals a surface labeling and a narrow contact to cortical thymocytes particularly in the peripheral cortical regions. An alternative staining pattern is realized by antibodies to some antigens associated with other subtypes of thymic epithelial cells. Medullary epithelial cells as well as the cortical surface epithelium react likewise positively with antibodies to special surface antigens (anti-Ep-1), to special epitopes of cytokeratin (anti-IV/82), and to thymic hormones (anti-FTS). The functional significance of distinct microenvironments within the thymus provided by different epithelial cells is discussed in view of the maturation of T-precursor cells.Glossary of Abbreviations
Anti-X
anti-X antibody
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APUD-cells
amine precursor uptake and decarboxylation (gastro-intestinal endocrine cells)
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DAB
diamino-benzidine
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DMSO
dimethyl sulfoxide
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FTS
facteur thymique sérique
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HLA-A, B, C
human leucocyte antigen, A, B, C-region related
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HLA-DR
human leucocyte antigen, D-region related
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IDC
interdigitating cell
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MHC
major histocompatibility gene complex
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PBS
phosphate-buffered saline
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TNC
thymic nurse cell
This investigation was supported by grants from the Deutsche Forschungsgemeinschaft, and its Sonderforschungsbereich 111Fellow of the Alexander von Humbold-Stiftung, Institute of Pathology, University of Würzburg, Federal Republic of GermanyThe authors appreciate the contribution of human thymus tissue from Professor Alexander Bernhard, Abteilung kardiovasculäre Chirurgie der Universität Kiel; the gift of monoclonal antibodies from Dr. M.J.D. Anderson, Dr. M. Dardenne and Dr. H.J. Radzun; and the excellent technical assistence of Mrs. O.M. Bracker, Mrs. H. Hansen, Mrs. R. Köpke, Mrs. M. v. Kolszynski, Mrs. J. Quitzau, Mrs. H. Siebke, and Mrs. H. Waluk 相似文献
930.
The complete three-dimensional structure in methanol of an amphipathic alpha-helical peptide, that has been designed by taking into account the three-dimensional structures of small haemolytic peptides, secondary structure prediction algorithms and the well documented literature on alpha-helix stabilizing factors, has been elucidated by two-dimensional NMR spectroscopy. Initially various two-dimensional spectra (COSY, TOCSY, and NOESY) allowed the complete sequence specific assignment of all signals in the 1H spectrum. Consequently trial structures were generated which were then subjected to molecular dynamics simulations using 121 NOE-derived distances and 25 vicinal coupling constant values as structural restraints to give a final set of calculated structures. These structures are in complete agreement with the results of a circular dichroism study and reveal that the peptide adopted a highly ordered alpha-helical conformation. Details of the structure which throw light on future peptide/protein design are discussed. 相似文献