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21.
Transport and Partitioning of CO(2) Fixed by Root Nodules of Ureide and Amide Producing Legumes 总被引:2,自引:2,他引:0
Nodulated and denodulated roots of adzuki bean (Vigna angularis), soybean (Glycine max), and alfalfa (Medicago sativa) were exposed to 14CO2 to investigate the contribution of nodule CO2 fixation to assimilation and transport of fixed nitrogen. The distribution of radioactivity in xylem sap and partitioning of carbon fixed by nodules to the whole plant were measured. Radioactivity in the xylem sap of nodulated soybean and adzuki bean was located primarily (70 to 87%) in the acid fraction while the basic (amino acid) fraction contained 10 to 22%. In contrast, radioactivity in the xylem sap of nodulated alfalfa was primarily in amino acids with about 20% in organic acids. Total ureide concentration was 8.1, 4.7, and 0.0 micromoles per milliliter xylem sap for soybean, adzuki bean, and alfalfa, respectively. While the major nitrogen transport products in soybeans and adzuki beans are ureides, this class of metabolites contained less than 20% of the total radioactivity. When nodules of plants were removed, radioactivity in xylem sap decreased by 90% or more. Pulse-chase experiments indicated that CO2 fixed by nodules was rapidly transported to shoots and incorporated into acid stable constituents. The data are consistent with a role for nodule CO2 fixation providing carbon for the assimilation and transport of fixed nitrogen in amide-based legumes. In contrast, CO2 fixation by nodules of ureide transporting legumes appears to contribute little to assimilation and transport of fixed nitrogen. 相似文献
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Gunter Saunders Mark E. Rogers Maxwell W. Adlard Geoffrey Holt 《Molecular & general genetics : MGG》1984,194(1-2):343-345
Summary High molecular weight DNA extracted from Penicillium chrysogenum has been fractionated using RPC-5 Analog, into three distinct types designated 1, 2 and 3. Types 1 and 2 have the same buoyant density of 1.710 g/cm3 and together appear to comprise the nuclear DNA. Type 1 is enriched for repeated sequences which are normally observed in restriction digests of P. chrysogenum total DNA. Conversely, type 2 appears to be composed entirely of non-repetitive sequences. Type 3 has been identified as mitochondrial DNA, having a buoyant density of 1.695 g/cm3 and an estimated molecular weight of 31.6×106 Daltons. 相似文献
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Expression of epidermal growth factor receptor and associated glycoprotein on cultured human brain tumor cells 总被引:3,自引:0,他引:3
P A Steck G E Gallick S A Maxwell W S Kloetzer R B Arlinghaus R P Moser J U Gutterman W K Yung 《Journal of cellular biochemistry》1986,32(1):1-10
The expression of epidermal growth factor (EGF-R) in normal glial and glioma cells grown in culture was examined by using several independent assays. Immunoprecipitation with the monoclonal antibody R1 of extracts from metabolically labeled glial and glioma cells revealed a protein of Mr approximately 170,000, with a migration in sodium dodecyl sulfate-polyacrylamide gels identical to the EGR-R of A431 epidermal carcinoma cells. Furthermore, in the majority of glioma extracts, a protein of Mr approximately 190,000 was specifically immunoprecipitated by this antibody. Similar results were obtained by immunoblotting with a second antibody directed against a synthetic peptide in the sequence of the v-erb-B oncogene. In cell lines expressing both proteins, each was specifically phosphorylated on tyrosine in immune complex kinase assays. The majority of glioma cells bound between 40,000 to 80,000 125I-labeled epidermal growth factor molecules per cell. These results suggest that the expression of EGF-R is common in cultured human glioma cells. In addition, a structurally related protein, is expressed in some of these cells. 相似文献
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Christian J. Le Peuch Danielle A.M. Le Peuch Sidney Katz Jacques G. Demaille Maxwell T. Hincke R. Bredoux J. Enouf S. Levy-Toledano Jacques Caen 《生物化学与生物物理学报:生物膜》1983,731(3):456-464
Calcium-accumulating vesicles were isolated by differential centrifugation of sonicated platelets. Such vesicles exhibit a activity of about 10 nmol (min·mg)?1 and an ATP-dependent Ca2+ uptake of about 10 nmol (min·mg)?1. When incubated in the presence of Mg[γ-32P]ATP, the pump is phosphorylated and the acyl phosphate bond is sensitive to hydroxylamine. The [32P]phosphate-labeled Ca2+ pump exhibits a subunit molecular weight of 120 000 when analyzed by lithium dodecyl sulfate-polyacrylamide gel electrophoresis. Platelet calcium-accumulating vesicles contain a 23 kDa membrane protein that is phosphorylatable by the catalytic subunit of cAMP-dependent protein kinase but not by protein kinase C. This phosphate acceptor is not phosphorylated when the vesicles are incubated in the presence of either Ca2+ or Ca2+ plus calmodulin. The latter protein is bound to the vesicles and represents 0.5% of the proteins present in the membrane fraction. Binding of 125I-labeled calmodulin to this membrane fraction was of high affinity (16 nM), and the use of an overlay technique revealed four major calmodulin-binding proteins in the platelet cytosol (). Some minor calmodulin-binding proteins were enriched in the membrane fractions (). When the vesicles are phosphorylated in the presence of MgATP and of the catalytic subunit of cAMP-dependent protein kinase, the rate of Ca2+ uptake is essentially unaltered, while the Ca2+ capacity is diminished as a consequence of a doubling in the rate of Ca2+ efflux. Therefore, the inhibitory effect of cAMP on platelet function cannot be explained in such simple terms as an increased rate of Ca2+ removal from the cytosol. Calmodulin, on the other hand, was observed to have no effect on the initial rate of calcium efflux when added either in the absence or in the presence of the catalytic subunit of the cyclic AMP-dependent protein kinase, nor did the addition of 0.5 μM calmodulin result in increased levels of vesicle phosphorylation. 相似文献
27.
The geochemistry of terpenoids and steroids 总被引:5,自引:0,他引:5
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Cyclophosphamide, given in widely spaced doses, was used in the treatment of a patient with pemphigus vulgaris and a patient with bullous pemphigoid. To our knowledge, this form of therapy has not previously been reported in these two diseases. The distinct advantages of the larger intermittent dose method of cyclophosphamide therapy over the more conventional daily dose regimen are discussed. 相似文献
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