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排序方式: 共有475条查询结果,搜索用时 15 毫秒
1.
Elli Kohen Cahide Kohen Joseph G. Hirschberg Alain W. Wouters Bo Thorell 《Biochimica et Biophysica Acta (BBA)/Molecular Cell Research》1982,720(4):420-424
A microspectrofluorimetric study is made of the influence of dimethylnitrosamine on NADP reduction, following sequential microinjections into the same L cell, of two substrates: (1) isocitrate, with activity of isocitrate dehydrogenase both in the extramitochondrial and intramitochondrial compartments, (2) 6-phosphogluconate, with activity of the dehydrogenase in the extramitochondrial compartment. In control L cells a two-step reduction of NAD(P) is obtained followed by relatively slow reoxidation. In the minutes which follow addition of carcinogen, e.g., dimethylnitrosamine, to the cell medium the isocitrate and 6-phosphogluconate-induced transient NADP reoxidation is decreased in magnitude compared to control, while the rate constant of NADPH reoxidation is considerably accelerated, possibly due to requirements at the level of the microsomal metabolizing system. Observations within the first hour of carcinogen addition suggest an interesting system for evaluating the immediate actions of carcinogens at extranuclear sites: i.e., a comparative study of NADP reduction-reoxidation rate constants via injection of substrates for extra- vs. intramitochondrial pathways. 相似文献
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Richard B. Pouw Mieke C. Brouwer Judy Geissler Laurens V. van Herpen Sacha S. Zeerleder Walter A. Wuillemin Diana Wouters Taco W. Kuijpers 《PloS one》2016,11(3)
The major human complement regulator in blood, complement factor H (FH), has several closely related proteins, called FH-related (FHR) proteins. As all FHRs lack relevant complement regulatory activity, their physiological role is not well understood. FHR protein 3 (FHR-3) has been suggested to compete with FH for binding to Neisseria meningitidis, thereby affecting complement-mediated clearance. Clearly, the in vivo outcome of such competition greatly depends on the FH and FHR-3 concentrations. While FH levels have been established, accurate FHR-3 levels were never unequivocally reported to date. Moreover, CFHR3 gene copy numbers commonly vary, which may impact the FHR-3 concentration. Hence, we generated five anti-FHR-3 mAbs to specifically measure FHR-3 in human healthy donors of which we determined the gene copy number variation at the CFH/CFHR locus. Finally, we examined the acute-phase response characteristics of FHR-3 in a small sepsis cohort. We determined FHR-3 levels to have a mean of 19 nM and that under normal conditions the copy number of CFHR3 correlates to a very large extent with the FHR-3 serum levels. On average, FHR-3 was 132-fold lower compared to the FH concentration in the same serum samples and FHR-3 did not behave as a major acute phase response protein. 相似文献
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Photoaffinity probes for serotonin and histamine receptors. Synthesis and characterization of two azide analogues of ketanserin 总被引:2,自引:0,他引:2
W Wouters J Van Dun J E Leysen P M Laduron 《The Journal of biological chemistry》1985,260(14):8423-8429
Two azide analogues of ketanserin (6- and 7-azido-3-[2- [4-(4-fluorobenzoyl)-1-piperidinyl]ethyl]-2, 4(1H,3H)-quinazolinedione) were synthesized and tested as possible photoaffinity probes for serotonin-S2 and histamine-H1 receptors. In reversible binding experiments, the azides showed high affinity for both receptor types. When membrane preparations were incubated with nanomolar concentrations of 7-azidoketanserin and subsequently irradiated with UV light, both serotonin and histamine receptors became irreversibly blocked. This irreversible binding was dependent on azide concentrations and time of irradiation and did not change in the presence of the scavenger p-aminobenzoic acid. In contrast, irreversible blockade at low concentrations of 6-azidoketanserin was only obtained for histamine receptors. However, this blockade was abolished by addition of the scavenger p-aminobenzoic acid indicating that it was not due to a real photoaffinity mechanism. In the rat prefrontal cortex, irreversible blocking of serotonin receptors with 7-azidoketanserin could be inhibited by serotonin agonists or antagonists but not by histaminergic compounds. On the contrary, in the guinea pig cerebellum, inactivation of histamine receptors could be inhibited by histamine antagonists and histamine itself but not by serotonergic compounds. This provides a way for differential photolabeling of either of these receptors. 相似文献
6.
Mobilization of a Recombinant IncQ Plasmid between Bacteria on Agar and in Soil via Cotransfer or Retrotransfer 总被引:3,自引:2,他引:1 下载免费PDF全文
Mobilization of a genetically engineered IncQ plasmid, pSKTG, was studied in vitro and in sterile and nonsterile soils. In biparental and triparental filter matings, the mobilization frequencies of pSKTG were identical, and the plasmid was mobilized only in the presence of self-transmissible plasmid RP4p. In sterile soil, mobilization was probably limited by reduced cell-to-cell contact, since the frequencies of mobilization were approximately 100-fold lower than the frequencies in the filter matings. The transfer frequency of pSKTG in sterile soil when RP4p was present in the same strain was about 100-fold higher than the transfer frequency when RP4p was present in a separate strain. In studies in natural soil, pSKTG was also found to be transferred to indigenous bacteria. However, natural mobilization by genetic elements present in the indigenous soil microflora could not be detected. In vitro studies of natural transfer suggested that such genetic elements occur in soil bacteria. 相似文献
7.
Wouters J. T. M. Driehuis F. L. Polaczek P. J. van Oppenraay Marie-Louise H. A. van Andel J. G. 《Antonie van Leeuwenhoek》1980,46(4):353-362
Populations of a Escherichia coli K 12 strain, containing the vector plasmid p BR 322, were grown in chemostat culture under glucose- and phosphatelimited conditions. Resistance to tetracycline and ampicillin were lost after prolonged cultivation, resulting in the production of apparent plasmid-free populations which were more competitive than the original population. This competitiveness between plasmid-free and plasmid-containing populations was greatest in environments where the nutrient restriction was severe. Also during sequential subcultivation in batch cultures loss of plasmid was observed. 相似文献
8.
Construction and characterization of mutants impaired in the biosynthesis of the K88ab antigen 总被引:26,自引:8,他引:18 下载免费PDF全文
Plasmid pFM205 contains the genetic determinant for the K88ab antigen and is composed of a 4.3-megadalton DNA fragment derived from wild-type K88ab plasmid pRI8801 and cloning vehicle pBR322. The K88 NA of pFM205 contains five genes, which code for polypeptides with apparent molecular weights of 17,000, 26,000 (the K88ab subunit), 27,000 27,500, and 81,000. All five polypeptides were synthesized as precursors approximately 2,000 daltons larger than the mature polypeptides, indicating that they are transported across the cytoplasmic membrane by means of a signal sequence. A set of deletion derivatives of pFM205 was constructed, each containing a deletion in one of the five genes. In strains harboring derivatives of pFM205 containing a deletion in the gene for the 17,000- or 81,000-dalton polypeptide, the K88ab subunit was synthesized and transported to the outside of the cell. However, these strains did not adhere to brushborders or guinea pig erythrocytes, suggesting that the K88ab subunits were not assembled into normal fimbriae. Strains harboring plasmids containing a deletion in the gene for the 27,500-dalton polypeptide still adhered to brush borders and guinea pig erythrocytes, although very little K88ab antigen could be detected with an immunological assay. In strains harboring plasmids containing a deletion in the gene for the 27,000-dalton polypeptide, the K88ab subunit was synthesized but was probably subsequently degraded rapidly. 相似文献
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Dale G. Nimmo Sarah Avitabile Sam C. Banks Rebecca Bliege Bird Kate Callister Michael F. Clarke Chris R. Dickman Tim S. Doherty Don A. Driscoll Aaron C. Greenville Angie Haslem Luke T. Kelly Sally A. Kenny Jos J. Lahoz‐Monfort Connie Lee Steven Leonard Harry Moore Thomas M. Newsome Catherine L. Parr Euan G. Ritchie Kathryn Schneider James M. Turner Simon Watson Martin Westbrooke Mike Wouters Matthew White Andrew F. Bennett 《Biological reviews of the Cambridge Philosophical Society》2019,94(3):981-998
Movement is a trait of fundamental importance in ecosystems subject to frequent disturbances, such as fire‐prone ecosystems. Despite this, the role of movement in facilitating responses to fire has received little attention. Herein, we consider how animal movement interacts with fire history to shape species distributions. We consider how fire affects movement between habitat patches of differing fire histories that occur across a range of spatial and temporal scales, from daily foraging bouts to infrequent dispersal events, and annual migrations. We review animal movements in response to the immediate and abrupt impacts of fire, and the longer‐term successional changes that fires set in train. We discuss how the novel threats of altered fire regimes, landscape fragmentation, and invasive species result in suboptimal movements that drive populations downwards. We then outline the types of data needed to study animal movements in relation to fire and novel threats, to hasten the integration of movement ecology and fire ecology. We conclude by outlining a research agenda for the integration of movement ecology and fire ecology by identifying key research questions that emerge from our synthesis of animal movements in fire‐prone ecosystems. 相似文献