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排序方式: 共有158条查询结果,搜索用时 15 毫秒
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M Denis A Wilhelmsson S Cuthill L Poellinger J A Gustafsson 《Biochemical and biophysical research communications》1989,163(1):444-451
The rat hepatic glucocorticoid, dioxin and oxysterol receptors were subjected to high performance liquid chromatography on size-exclusion and anion-exchange columns. Both the glucocorticoid receptor and the dioxin receptor had a Stokes radius Rs approximately 7.5 nm, expected value for heteromeric complexes containing a dimer of the Mr approximately 90,000 heat shock protein, hsp90 (Rs approximately 7.0 nm). The oxysterol receptor represented a much smaller entity (Rs approximately 6.0 nm). When analyzed on a Mono Q anion-exchange column, the molybdate-stabilized glucocorticoid receptor and dioxin receptor eluted as single peaks at approximately 0.30 M and 0.26-0.28 M NaCl, respectively, whereas the oxysterol receptor represented a less negatively charged species (0.11-0.14 M NaCl). Following washing of the Mono Q column with molybdate-free buffer, the activated monomeric glucocorticoid receptor was detected (0.10-0.12 M NaCl). In contrast, no modification in the elution pattern of the dioxin receptor and the oxysterol receptor was observed. These data demonstrate differences in the physico-chemical properties of the glucocorticoid, dioxin and oxysterol receptors, respectively, which might reflect structural differences. 相似文献
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Detecting non-neutral heterogeneity across a region of DNA sequence in the ratio of polymorphism to divergence 总被引:11,自引:4,他引:7
Natural selection, in the form of balancing selection or selective sweeps,
can result in a decoupling of the amounts of molecular polymorphism and
divergence. Thus natural selection can cause some areas of DNA sequence to
have greater silent polymorphism, relative to divergence between species,
than other areas. It would be useful to have a statistical test for
heterogeneity in the polymorphism to divergence ratio across a region of
DNA sequence, one that could identify heterogeneity greater than that
expected from the neutral processes of mutation, drift, and recombination.
The only currently available test requires that a region be arbitrarily
divided into sections that are compared with each other, and the
subjectivity of this division could be problematic. Here a test is proposed
in which runs of polymorphic and fixed sites are counted, where a "run" is
a set of one or more sites of one type preceded and followed by the other
type. The number of runs is smaller than otherwise expected if
polymorphisms are clumped together. By simulating neutral evolution and
comparing the observed number of runs to the simulations, a statistical
test is possible which does not require any a priori decisions about
subdivision.
相似文献
5.
Activation of the dioxin and glucocorticoid receptors to a DNA binding state under cell-free conditions 总被引:8,自引:0,他引:8
T Nemoto G G Mason A Wilhelmsson S Cuthill J Hapgood J A Gustafsson L Poellinger 《The Journal of biological chemistry》1990,265(4):2269-2277
The activation in vitro of dioxin and glucocorticoid receptors from a non-DNA binding to a DNA binding state was characterized. Ligand-free dioxin and glucocorticoid receptors were partially co-purified from rat liver cytosol, and both receptors sedimented at 9 S following labeling with the respective ligand. The 9 S forms of the dioxin and glucocorticoid receptors have previously been shown to represent heteromeric complexes containing the Mr approximately equal to 90,000 heat shock protein. The 9 S ligand-free or ligand-bound glucocorticoid receptor was converted to the monomeric 4-5 S form upon exposure to 0.4 M NaCl even in the presence of the stabilizing agent molybdate. Under identical conditions, the 9 S ligand-free and ligand-bound dioxin receptor forms remained essentially intact. However, in the absence of molybdate, the dioxin receptor could be converted to a 4-5 S form upon exposure to high concentrations of salt. These results indicate that the glucocorticoid receptor readily dissociates from the 9 S to the 4-5 S form even in the absence of hormone, whereas both the ligand-free and ligand-occupied 9 S dioxin receptor forms represent more stable species. Gel mobility shift experiments revealed that the 4-5 S glucocorticoid receptor interacted with a glucocorticoid response element both in the absence and presence of ligand. On the other hand, occupation of the dioxin receptor by ligand greatly enhanced the ability of the receptor to be activated to a form that binds to its target enhancer element. Once dissociated, the monomeric form of the dioxin receptor was also able to interact with its DNA target sequences even in the absence of ligand. Thus, ligand binding efficiently facilitates subunit dissociation of the dioxin receptor but is not a prerequisite for DNA binding per se. Given the apparent stability of its non-DNA binding 9 S form, the dioxin receptor system might be a useful model for the investigation of the mechanism of activation of soluble receptor proteins. 相似文献
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Janine JH Oosterhof G Jolanda Elving Ietse Stokroos Arie van nieuw Amerongen Henny C van der Mei Henk J Busscher 《Biofouling》2013,29(6):347-353
The integrity of biofilms on voice prostheses used to rehabilitate speech in laryngectomized patients causes unwanted increases in airflow resistance, impeding speech. Biofilm integrity is ensured by extracellular polymeric substances (EPS). This study aimed to determine whether synthetic salivary peptides or mucolytics, including N-acetylcysteine and ascorbic acid, influence the integrity of voice prosthetic biofilms. Biofilms were grown on voice prostheses in an artificial throat model and exposed to synthetic salivary peptides, mucolytics and two different antiseptics (chlorhexidine and Triclosan). Synthetic salivary peptides did not reduce the air flow resistance of voice prostheses after biofilm formation. Although both chlorhexidine and Triclosan reduced microbial numbers on the prostheses, only the Triclosan-containing positive control reduced the air flow resistance. Unlike ascorbic acid, the mucolytic N-acetylcysteine removed most EPS from the biofilms and induced a decrease in air flow resistance. 相似文献
9.
Pearn SM Bennett AT Cuthill IC 《Proceedings. Biological sciences / The Royal Society》2003,270(1517):859-865
Fluorescence has so far been found in 52 parrot species when illuminated with ultraviolet-A (UVA) 'black' lamps, and two attempts have been made to determine whether such fluorescence plays any role in sexual signalling. However, the contribution of the reflectance versus fluorescence to the total radiance from feathers, even in the most studied species to date (budgerigars), is unclear. Nor has the plumage of this study species been systematically assessed to determine the distribution of fluorescent patches. We therefore used spectrofluorometry to determine which areas of budgerigars fluoresce and the excitation and emission spectra involved; this is the first time that such a technique has been applied to avian plumage. We found that both the yellow crown and (normally hidden) white downy chest feathers exhibit strong UVA-induced fluorescence, with peak emissions at 527 nm and 436 nm, respectively. Conversely, the bright-green chest and dark-blue tail feathers do not fluoresce. When comparing reflectance spectra (400-700 nm) from the yellow crown using illuminants with a proportion of UVA comparable to daylight, and illuminants with all UVA removed, no measurable difference resulting from fluorescence was found. This suggests that under normal daylight the contribution of fluorescence to radiance is probably trivial. Furthermore, these spectra revealed that males had fluorescent crowns with substantially higher reflectance than those of females, in both the UV waveband and at longer wavelengths. Reflectance spectrophotometry was also performed on a number of live wild-type male budgerigars to investigate the chromatic contrast between the different plumage areas. This showed that many plumage regions are highly UV-reflective. Overall our results suggest that rapid surveys using UVA black lamps may overestimate the contribution of fluorescence to plumage coloration, and that any signalling role of fluorescence emissions, at least from the yellow crown of budgerigars, may not be as important as previously thought. 相似文献
10.
The optimal amount of reserves that a small bird should carry depends upon a number of factors, including the availability of food and environmental predation risk levels. Theory predicts that, if predation risk increases, then a bird should maintain a lower level of reserves. Previous experiments have given mixed results: some have shown reduced reserves and some, increased reserves. However, the birds in these studies may have been interpreting a staged predation event as a period when they were unable to feed rather than a change in predation risk: theory predicts that, if the food supply within the environment is variable, then reserves should be increased. In the present study, we presented blue tits (Parus caeruleus) with a potential predator and compared this response (which could have been potentially confounded by perceived interruption effects) with a response to an actual interruption in the environment during both long and short daytime lengths. During long (but not short) days, the birds responded in line with theoretical predictions by increasing their reserves in response to interruption and reducing them in response to predation. These results are examined in the light of other experimental manipulations and we discuss how well experimental tests have tested the predictions made by theoretical models. 相似文献