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1.
St-Onge MP 《Obesity (Silver Spring, Md.)》2010,18(11):2067-2068
Data from National Health and Nutrition Examination Surveys (NHANES) 1999-2004 have recently shown the percent body fat of American adults. Average American men and women have ~28 and 40% body fat. When categorized by BMI and age, the data also show high percent body fat values, particularly in lower BMI categories. These data should make one reflect on the health status of Americans in all BMI categories and the use of these data for public health recommendations. 相似文献
2.
The α-sheet has been speculated to play a role as a toxic conformer in amyloid diseases. However, except for relatively short fragments, its detection has remained elusive. Here, we present molecular dynamics simulations that support the existence of the α-sheet as a stable, metastable, or long-lived secondary structure in polyglutamine and, to a lesser extent, in polyasparagine aggregates. 相似文献
3.
Do some deep‐sea,sediment‐dwelling species of harpacticoid copepods have 1000‐km‐scale range sizes?
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The range sizes of sediment‐dwelling deep‐sea species are largely unknown. Such knowledge is important because a deep sea composed in large part of species with 100‐km‐scale ranges would be very different from one composed predominantly of species with 1000‐km‐scale ranges. For example, the total species richness would be much greater in the first case than in the second. As a step towards the determination of the distribution of species’ range sizes in the deep sea, we asked whether harpacticoid copepods (Crustacea) on the continental rise in the northeastern Pacific had 1000‐km‐scale range sizes. We chose harpacticoids because they occur widely in deep‐sea sediments and thus are a typical deep‐sea taxon. In addition, they have no pelagic stage in their life history, so they allow a conservative test of hypotheses about species’ range sizes. We used morphology and gene‐sequence data to assign individuals to species. At least 13.3% of the species we studied had 1000‐km‐scale ranges, raising the question of how these species maintain genetic continuity. 相似文献
4.
Is there safety‐in‐numbers for prey? 总被引:4,自引:0,他引:4
Sean D. Connell 《Oikos》2000,88(3):527-532
The abundance of prey affects the rate of predation, but little consensus exists on whether this enhances or reduces per capita mortality. Studies of aggregating prey in marine habitats generally emphasise that the probability of predation of any individual is the reciprocal of the number of prey within a school. A field experiment tested the alternative hypotheses that predation by predatory fish on schooling prey (1) increased with an increase in the number of prey per school and that this caused (2) survival to be lower in schools with more individuals. The number of prey (juvenile Acanthochromis polyacanthus ) per school was manipulated in replicate treatments with natural densities of large predatory fish (open plots) and treatments without large predatory fish (exclusion cages). Large predatory fish preyed on juveniles in a density-dependent manner and this was the key source of density-dependent mortality in plots open to all predators. There was some suggestion that small predatory fish also prey on juveniles in a density-dependent manner, but this was weak and did not translate into density-dependent mortality of juveniles. It would appear that aggregation of prey may be a successful strategy against predation from some predators, but not always every predator, or all predators in combination. 相似文献
5.
4-Hydroxy-2,3-trans-nonenal (HNE) is a neurotoxic unsaturated aldehyde end-product of lipid peroxidation. The addition of HNE to NT-2 and SK-N-MC cell lines induces apoptosis and we now investigated the time-course of events occurring prior to apoptosis. Treatment of both NT-2 and SK-N-MC cell lines with HNE led to HNE association with the proteasome, increased levels of protein carbonyls and ubiquitinated proteins, and decreased proteasomal function. There was also decreased metabolic activity, cytochrome c release and activation of caspase 3, followed by apoptotic changes including chromatin condensation, cell shrinkage and DNA fragmentation and laddering. Overexpression of mutant superoxide dismutase 1 proteins associated with amyotrophic lateral sclerosis decreased proteasomal activities in the absence of HNE and accelerated the apoptosis induced by HNE. By contrast, overexpression of wild-type superoxide dismutase 1 did not affect basal levels of proteasomal activity. The data suggest that accumulation of ubiquitinated proteins and impairment of proteasomal function are important events in HNE toxicity. We propose that the proteasomal system is a significant target of HNE neurotoxicity in a wide range of neurodegenerative diseases, especially if abnormal proteins are being expressed. 相似文献
6.
Agns Anne Christian Bourdillon Sandra Daninos Jacques Moiroux 《Biotechnology and bioengineering》1999,64(1):101-107
The inversion of configuration of L‐alanine can be carried out by combining its selective oxidation in the presence of NAD+ and L‐alanine dehydrogenase, electrochemical regeneration of the NAD+ at a carbon felt anode, and reductive amination of pyruvate, i.e., reduction of its imino derivative at a mercury cathode, the reaction mixture being buffered with concentrated ammonium/ammonia (1.28M / 1.28M). The dehydrogenase exhibits astonishing activity and stability under such extreme conditions of pH and ionic strength. The main drawback of the process is its slowness. At best, the complete inversion of a 10 mM solution of L‐alanine requires 140 h. A careful and detailed quantitative analysis of each of the key steps involved shows that the enzyme catalyzed oxidation is so thermodynamically uphill that it can be driven efficiently to completion only when both the coenzyme regeneration and the pyruvate reduction are very effective. The first condition is easily fulfilled. Under the best conditions, it is the rate of the chemical reaction producing the imine which controls the whole process kinetically. © 1999 John Wiley & Sons, Inc. Biotechnol Bioeng 64: 101–107, 1999. 相似文献
7.
Florian Gourgue Lionel Mignion Matthias Van Hul Natacha Dehaen Estelle Bastien Valery Payen Baptiste Leroy Nicolas Joudiou Didier Vertommen Caroline Bouzin Nathalie Delzenne Bernard Gallez Olivier Feron Bndicte F. Jordan Patrice D. Cani 《Journal of cellular and molecular medicine》2020,24(17):10233-10244
Epidemiological studies have shown that obese subjects have an increased risk of developing triple‐negative breast cancer (TNBC) and an overall reduced survival. However, the relation between obesity and TNBC remains difficult to understand. We hypothesize that apelin, an adipokine whose levels are increased in obesity, could be a major factor contributing to both tumour growth and metastatization in TNBC obese patients. We observed that development of obesity under high‐fat diet in TNBC tumour‐bearing mice significantly increased tumour growth. By showing no effect of high‐fat diet in obesity‐resistant mice, we demonstrated the necessity to develop obesity‐related disorders to increase tumour growth. Apelin mRNA expression was also increased in the subcutaneous adipose tissue and tumours of obese mice. We further highlighted that the reproduction of obesity‐related levels of apelin in lean mice led to an increased TNBC growth and brain metastases formation. Finally, injections of the apelinergic antagonist F13A to obese mice significantly reduced TNBC growth, suggesting that apelinergic system interference could be an interesting therapeutic strategy in the context of obesity and TNBC. 相似文献
8.
Samantha P. Klaus Lauren P. Fitzsimmons Trevor E. Pitcher Susan M. Bertram 《Ethology : formerly Zeitschrift fur Tierpsychologie》2011,117(2):154-162
When females mate multiply (polyandry) both pre‐ and post‐copulatory sexual selection can occur. Sperm competition theory predicts there should be a trade‐off between investment in attracting mates and investment in ejaculate quality. In contrast, the phenotype‐linked fertility hypothesis predicts a positive relationship should exist between investment in attracting mates and investment in ejaculate quality. Given the need to understand how pre‐ and post‐copulatory sexual selection interacts, we investigated the relationship between secondary sexual traits and ejaculate quality using the European house cricket, Acheta domesticus. Although we found no direct relationship between cricket secondary sexual signals and ejaculate quality, variation in ejaculate quality was dependent on male body weight and mating latency: the lightest males produced twice as many sperm as the heaviest males but took longer to mate with females. Our findings are consistent with current theoretical models of sperm competition. Given light males may have lower mating success than heavy males because females take longer to mate with them in no‐choice tests, light males may be exhibiting an alternative reproductive tactic by providing females with more living sperm. Together, our findings suggest that the fitness of heavy males may depend on pre‐copulatory sexual selection, while the fitness of light males may depend on post‐copulatory fertilization success. 相似文献
9.
Male genes: X‐pelled or X‐cluded? 总被引:3,自引:0,他引:3
Rogers DW Carr M Pomiankowski A 《BioEssays : news and reviews in molecular, cellular and developmental biology》2003,25(8):739-741
Two recent studies by Parisi et al. and Ranz et al., catalogue sex differences in gene expression across the whole genome of the fruit fly Drosophila melanogaster. Both report striking associations of sex-biased gene expression with the X chromosome. Genes with male-biased expression are depauperate on the X chromosome, whereas genes with female-biased expression show weaker evidence of being in excess. A number of evolutionary hypotheses for the expulsion or exclusion of male-biased genes from the X chromosome have been suggested. None is entirely consistent with the available evidence. 相似文献
10.
Was Archaeopteryx a wing‐in‐ground effect flier? 总被引:1,自引:0,他引:1
11.
New Zealand's (NZ) geographical isolation, extensive coastline and well-characterized oceanography offer a valuable system for marine biogeographical research. Here we use mtDNA control region sequences in the abundant endemic sea-star Patiriella regularis to test the following literature-based predictions: that coastal upwelling disrupts north-south gene flow and promotes population differentiation (hypothesis 1); and that an invasive Tasmanian population of the species was introduced anthropogenically from southern New Zealand (hypothesis 2). We sequenced 114 samples from 22 geographical locations, including nine sites from North Island, nine from South Island, one from Stewart Island and three from Tasmania. Our analysis of these sequences revealed an abundance of shallow phylogenetic lineages within P. regularis (68 haplotypes, mean divergence 0.9%). We detected significant genetic heterogeneity between pooled samples from northern vs. southern New Zealand (FST = 0.072; P = 0.0002), consistent with the hypothesis that upwelling disrupts gene flow between these regions (hypothesis 1). However, we are currently unable to rule out the alternative hypothesis that Cook Strait represents a barrier to dispersal (North Island vs. South Island; FST = 0.031; P = 0.0467). The detection of significant spatial structure in NZ samples is consistent with restricted gene flow, and the strong structure evident in northern NZ may be facilitated by distinct ocean current systems. Four shared haplotypes and nonsignificant differentiation (FST = 0.025; P = 0.2525) between southern New Zealand and Tasmanian samples is consistent with an anthropogenic origin for the latter population (hypothesis 2). 相似文献
12.
13.
Arne Traulsen 《Evolution; international journal of organic evolution》2010,64(2):316-323
Evolutionary game theory is a general mathematical framework that describes the evolution of social traits. This framework forms the basis of many multilevel selection models and is also frequently used to model evolutionary dynamics on networks. Kin selection, which was initially restricted to describe social interactions between relatives, has also led to a broader mathematical approach, inclusive fitness, that can not only describe social evolution among relatives, but also in group structured populations or on social networks. It turns out that the underlying mathematics of game theory is fundamentally different from the approach of inclusive fitness. Thus, both approaches—evolutionary game theory and inclusive fitness—can be helpful to understand the evolution of social traits in group structured or spatially extended populations. 相似文献
14.
Borregaard MK Gotelli NJ Rahbek C 《Evolution; international journal of organic evolution》2012,66(7):2216-2226
The concept of species-level heritability is widely contested. Because it is most likely to apply to emergent, species-level traits, one of the central discussions has focused on the potential heritability of geographic range size. However, a central argument against range-size heritability has been that it is not compatible with the observed shape of present-day species range-size distributions (SRDs), a claim that has never been tested. To assess this claim, we used forward simulation of range-size evolution in clades with varying degrees of range-size heritability, and compared the output of three different models to the range-size distribution of the South American avifauna. Although there were differences among the models, a moderate-to-high degree of range-size heritability consistently leads to SRDs that were similar to empirical data. These results suggest that range-size heritability can generate realistic SRDs, and may play an important role in shaping observed patterns of range sizes. 相似文献
15.
16.
Tsutomu Miyasaka Ashish Kulkarni Gyu Min Kim Senol
z Ajay K. Jena 《Liver Transplantation》2020,10(13)
Having demonstrated incredibly fast progress in power conversion efficiency, rising to a level comparable with that of crystalline silicon cells, lead‐based organic–inorganic hybrid perovskite solar cells are now facing the stability tests needed for industrialization. Poor thermal stability (<150 °C) owing to organic constituents and interlayer diffusion of materials (dopants), and environmental incompatibility due to Pb has surged the development of organic‐free, Pb‐free perovskites and dopant‐free hole transport materials (HTMs). The recent rapid increase in efficiency of cells based on inorganic perovskites, crossing 18%, demonstrates the great potential of inorganic perovskites as thermally stable and high‐efficiency cells. Although all kinds of Pb‐free perovskites lag in efficiency in comparison to the hybrid and inorganic perovskites, they also demonstrate better structural and environmental stability. The performance of dopant‐free HTMs matching/surpassing dopant‐containing HTMs makes the former a better choice for stability. Even though the efforts to enhance the stability of Pb‐based hybrid perovskites should continue by different techniques, organic‐free and lead‐free perovskites, and dopant‐free HTMs must be pursued with greater interest for the future. This review describes the present issues and possible strategies to address them, and thus will help to improve the overall performance of robust organic‐free, Pb‐free, and dopant‐free perovskite solar cells. 相似文献
17.
Vytas A Bankaitis 《The EMBO journal》2015,34(8):978-980
The breakdown of cellular components via autophagy is crucial for cellular homeostasis. In this issue of The EMBO Journal, Niso‐Santano et al ( 2015 ) report the important observation that feeding cells with saturated or unsaturated fatty acids triggers mechanistically distinct autophagic responses. Feeding cells saturated fatty acid induced the canonical, BECN1/PI3K‐dependent autophagy pathway. Conversely, the unsaturated fatty acid oleate triggered autophagic responses that were independent of the BECN1/PI3K complex, but that required a functional Golgi system. 相似文献
18.
High biodiversity is an important component of sustainable agricultural systems, and previous studies have found that increases in the diversity of the natural enemies of pests are associated with decreases in pest populations. Weaver ants are well known for their highly territorial and aggressive behaviour and for their control efficiency of many insect pests in tropical crop trees. Because of this, the ants have been used as a key component in integrated pest management (IPM) programmes for tropical crop trees. In implementing the IPM programmes, we received a number of enquiries related to whether weaver ants have negative effects on arthropod diversity and other natural enemies in orchard systems due to their aggressive behaviour. To answer these questions, we regularly sampled canopy arthropods in cashew and mango orchards in the Northern Territory of Australia in 1996, 2002 and 2003. We sampled, using a vacuum sampler, orchards with and without weaver ants. Cashew and mango plots with abundant weaver ants had similar or higher canopy arthropod and natural enemy diversity and similar ratios of natural enemies to insect pests, compared with plot where the weaver ant was absent. The study also showed that the application of insecticides reduced arthropod diversity and the ratio of natural enemies to insect pests in a mango orchard. However, insecticide spray did not affect natural enemy diversity and abundance, which may be related to a high immigration rate of natural enemies in small plots surrounded by areas that were not sprayed. 相似文献
19.
How do reaction conditions affect the enantiopure synthesis of 2‐substituted‐1,4‐benzodioxane derivatives?
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Several biologically active compounds structurally include the enantiopure 2‐substituted‐1,4‐benzodioxane scaffold. The straightforward racemization that affects reactions involving most of the common chemical reactives is thus a crucial issue. The developing of a completely stereo‐controlled synthetic route that does not affect the enantiomeric excess is consequently mandatory. It is also important to set up a reliable chiral HPLC method, able to follow the reaction, and to improve the synthetic performances. Here, we report the chiral investigation of two different synthons, we specifically evaluated the synthetic pathways that could be run in order to afford them, avoiding the racemization processes, which could normally occur in basic conditions. In addition, we developed peculiar chiral HPLC methods in order to resolve the enantiomers, define the enantiomeric excess, and fully characterize these compounds. 相似文献
20.
Quercetin and other flavonoids have been reported to exhibit both antioxidant and pro‐oxidant properties. Most studies about the pro‐oxidative ability were conducted in the presence of metal ions, and the essential functional moiety of quercetin responsible for the pro‐oxidative effect is still unclear. In this study, we evaluated the pro‐oxidative abilities in the absence of metal ions of two quercetin derivatives, i.e., quercetin‐3′‐O‐β‐D ‐glucoside ( 1 ) and quercetin‐3‐O‐β‐D ‐glucoside ( 2 ), by assessing DNA cleavage and HO.‐radical production. The binding mode between these compounds and DNA was studied by fluorescence and viscometric titrations. The results showed that 1 can efficiently induce oxidative damage to plasmid DNA, while 2 shows poor activity. Both 1 and 2 bind to DNA via groove‐binding. These results proved that the α‐hydroxy‐β‐oxo‐α,β‐enone moiety contributes to the pro‐oxidative activity of quercetin. 相似文献