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31.
Measurements of cytoplasmic and vacuolar pH in Neurospora using nitrogen-15 nuclear magnetic resonance spectroscopy 总被引:3,自引:0,他引:3
The nitrogen-15 chemical shift of the N1 (tau)-nitrogen of 15N-labeled histidine and the half-height line widths of proton-coupled resonances of the delta- and omega,omega'-nitrogens of 15N-labeled arginine and of the alpha-nitrogens of 15N-labeled alanine and proline were measured in intact mycelia of Neurospora crassa to obtain to estimates of intracellular pH. For intracellular 15N-labeled histidine, the N1 (tau)-nitrogen chemical shift was 200.2 ppm. In vitro measurements showed that the chemical shift was slightly affected by the presence of phosphate, with which the basic amino acids may be associated in vivo. These considerations indicate a pH of 5.7-6.0 for the environment of intracellular histidine. The half-height line widths of the delta- and omega,omega'-nitrogens of [15N]arginine were 15 and 26 Hz, respectively. In vitro studies showed that these line widths also are influenced by the presence of phosphate, and, after suitable allowance for this, the line widths indicate pH 6.1-6.5 for intracellular arginine. The half-height line widths for intracellular alanine and proline were 17 and 12 Hz, respectively, which are consistent with an intracellular pH of 7.1-7.2. Pools of histidine and arginine are found principally in the vacuole of Neurospora, most likely in association with polyphosphates. Proline and alanine are cytoplasmic. The results reported here are consistent with these localizations and indicate that the vacuolar pH is 6.1 +/- 0.4 while the cytoplasmic pH is 7.15 +/- 0.10. Comparisons of these estimates with those obtained by other techniques and their implications for vacuolar function are discussed. 相似文献
32.
Transcriptional regulatory network triggered by oxidative signals configures the early response mechanisms of japonica rice to chilling stress 总被引:3,自引:0,他引:3
33.
Recent studies have revealed an unexpected synergism between two seemingly unrelated protein families: CCN matricellular proteins
and the tumor necrosis factor (TNF) family of cytokines. CCN proteins are dynamically expressed at sites of injury repair
and inflammation, where TNF cytokines are also expressed. Although TNFα is an apoptotic inducer in some cancer cells, it activates
NFκB to promote survival and proliferation in normal cells, and its cytotoxicity requires inhibition of de novo protein synthesis
or NFκB signaling. The presence of CCN1, CCN2, or CCN3 overrides this requirement and unmasks the apoptotic potential of TNFα,
thus converting TNFα from a proliferation-promoting protein into an apoptotic inducer. These CCN proteins also enhance the
cytotoxicity of other TNF cytokines, including LTα, FasL, and TRAIL. Mechanistically, CCNs function through integrin α6β1 and the heparan sulfate proteoglycan (HSPG) syndecan-4 to induce reactive oxygen species (ROS) accumulation, which is essential
for apoptotic synergism. Mutant CCN1 proteins defective for binding α6β1-HSPGs are unable to induce ROS or apoptotic synergism with TNF cytokines. Further, knockin mice that express an α6β1-HSPG-binding defective CCN1 are blunted in TNFα- and Fas-mediated apoptosis, indicating that CCN1 is a physiologic regulator
of these processes. These findings implicate CCN proteins as contextual regulators of the inflammatory response by dictating
or enhancing the cytotoxicity of TNFα and related cytokines. 相似文献
34.
Background
Introductions of non-native tiger salamanders into the range of California tiger salamanders have provided a rare opportunity to study the early stages of secondary contact and hybridization. We produced first- and second-generation hybrid salamanders in the lab and measured viability among these early-generation hybrid crosses to determine the strength of the initial barrier to gene exchange. We also created contemporary-generation hybrids in the lab and evaluated the extent to which selection has affected fitness over approximately 20 generations of admixture. Additionally, we examined the inheritance of quantitative phenotypic variation to better understand how evolution has progressed since secondary contact. 相似文献35.
CHLOROPLASTS are more permeable to amino-acids1,2 than are cell membranes3 and also discriminate between their optical isomers2. This has led to the suggestion that the passage of amino-acids through the limiting membranes of chloroplasts is facilitated by carriers2. Using the additional criteria of saturation and competition, we support this suggestion and show that at least two carriers are probably involved. 相似文献
36.
The probability that protected areas will deliver their potential for maintaining or enhancing biodiversity is likely to be
maximised if they are appropriately and effectively managed. As a result, governments and conservation agencies are devoting
much attention to the management of protected areas. In the U.K., the demand for performance accountability has resulted in
Public Service Agreements (PSA) that set out targets for government departments to deliver results in return for investments
being made. One such target for England is to ensure that all nationally important wildlife sites are in favourable condition
by 2010. Here, we tested the hypothesis, of potential strategic importance, that the ecological condition of these sites is
predictable from relationships with a range of physical, environmental and demographic variables. We used binary logistic
regression to investigate these relationships, using the results of English Nature’s 1997–2003 condition assessment exercise.
Generally, sites in unfavourable condition tend to be larger in area, located at higher elevations, but with higher human
population density and are more spatially isolated from units of the same habitat. However, despite the range of different
parameters included in our models, the extent to which the condition of any given site could be predicted was low. Our results
have implications for the delivery of PSA targets, funding allocation, and the location of new protected areas. 相似文献
37.
Leslie A. Holladay Phillip Wilder 《Biochimica et Biophysica Acta (BBA)/General Subjects》1980,629(1):156-167
The effect of cationic, anionic and nonionic detergents on the EPR spectrum of spin-labeled somatostatin has been studied. At detergent concentrations well above the critical micelle concentration, nonionic detergents do not alter the EPR spectrum. Sodium dodecyl sulfate markedly alters both the line height ratio and the hyperfine splitting constant, whilst dodecyltrimethylammonium bromide alters only slightly the hyperfine splitting constant and line height ratio. The somatostatin-sodium dodecyl sulfate complex appeared monodisperse by sedimentation equilibrium with about 17 g bound detergent per g peptide. Circular dichroic and difference spectra of the dodecyl sulfate-somatostatin complex show that the tryptophanyl residue is buried in a nonpolar environment and that the secondary and tertiary structure of the peptide is markedly altered. Sedimentation equilibrium studies suggest that two types of dodecyltrimethylammonium-somatostatin complex exist. One type resembles the dodecyl sulfate-peptide complex, whilst the other appears to include several peptide units with only about one gram bound detergent per gram peptide. 相似文献
38.
Daren Lee Seth Ruffins Queenie Ng Nikhil Sane Steve Anderson Arthur Toga 《BMC bioinformatics》2010,11(1):608
Background
Digital atlases provide a common semantic and spatial coordinate system that can be leveraged to compare, contrast, and correlate data from disparate sources. As the quality and amount of biological data continues to advance and grow, searching, referencing, and comparing this data with a researcher's own data is essential. However, the integration process is cumbersome and time-consuming due to misaligned data, implicitly defined associations, and incompatible data sources. This work addressing these challenges by providing a unified and adaptable environment to accelerate the workflow to gather, align, and analyze the data. 相似文献39.
Maria João Feio Trefor B. Reynoldson Verónica Ferreira Manuel Augusto S. Graça 《Hydrobiologia》2007,579(1):55-68
We sampled macroinvertebrates at 75 locations in the Mondego river catchment, Central Portugal, and developed a predictive
model for water quality assessment of this basin, based on the Reference Condition Approach. Sampling was done from June to
September 2001. Fifty-five sites were identified as “Reference sites” and 20 sites were used as “Test sites” to test the model.
At each site we also measured 40 habitat variables to characterize water physics and chemistry, habitat type, land use, stream
hydrology and geographic location. Macroinvertebrates were generally identified to species or genus level; a total of 207
taxa were found. By Unweighted Pair Group Method with Arithmetic mean (UPGMA) clustering and analysis of species contribution
to similarities percentage (SIMPER), two groups of reference sites were established. Using Discriminant Analysis (stepwise
forward), four variables correctly predicted 78% of the reference sites to the appropriate group: stream order, pool quality,
substrate quality and current velocity. Test sites’ environmental quality was established from their relative distance to
reference sites, in MDS ordination space, using a series of bands (BEAST methodology). The model performed well at upstream
sites, but at downstream sites it was compromised by the lack of reference sites. As with the English RIVPACS predictive model,
the Mondego model should be continually improved with the addition of new reference sites. The adaptation of the Mondego model
methodology to the Water Framework Directive is possible and would consist mainly of the integration of the WFD typology and
increasing the number of ellipses that define quality bands.
Handling editor: K. Martens 相似文献
40.
Charles L. Nunn Peter H. Thrall Kelly Stewart Alexander H. Harcourt 《Evolutionary ecology》2008,22(4):519-543
Emerging infectious diseases threaten a wide diversity of animals, and important questions remain concerning disease emergence
in socially structured populations. We developed a spatially explicit simulation model to investigate whether—and under what
conditions—disease-related mortality can impact rates of pathogen spread in populations of polygynous groups. Specifically,
we investigated whether pathogen-mediated dispersal (PMD) can occur when females disperse after the resident male dies from
disease, thus carrying infections to new groups. We also examined the effects of incubation period and virulence, host mortality
and rates of background dispersal, and we used the model to investigate the spread of the virus responsible for Ebola hemorrhagic
fever, which currently is devastating African ape populations. Output was analyzed using regression trees, which enable exploration
of hierarchical and non-linear relationships. Analyses revealed that the incidence of disease in single-male (polygynous)
groups was significantly greater for those groups containing an average of more than six females, while the total number of
infected hosts in the population was most sensitive to the number of females per group. Thus, as expected, PMD occurs in polygynous
groups and its effects increase as harem size (the number of females) increases. Simulation output further indicated that
population-level effects of Ebola are likely to differ among multi-male–multi-female chimpanzees and polygynous gorillas,
with larger overall numbers of chimpanzees infected, but more gorilla groups becoming infected due to increased dispersal
when the resident male dies. Collectively, our results highlight the importance of social system on the spread of disease
in wild mammals. 相似文献