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排序方式: 共有223条查询结果,搜索用时 15 毫秒
91.
92.
Marcela Krečmerová Petr Jansa Martin Dračínský Petra Sázelová Václav Kašička Johan Neyts Joeri Auwerx Eleonóra Kiss Nesya Goris George Stepan Zlatko Janeba 《Bioorganic & medicinal chemistry》2013,21(5):1199-1208
New large-scale synthetic approach to antiretroviral agent 9-[2-(R)-(phosphonomethoxy)propyl]-2,6-diaminopurine, (R)-PMPDAP, was developed. Reaction of (R)-propanediol carbonate with 2,6-diaminopurine afforded exclusively (R)-9-(2-hydroxypropyl)-2,6-diaminopurine which was subsequently used for introduction of a phosphonomethyl residue using TsOCH2P(O)(OiPr)2 or BrCH2P(O)(OiPr)2 followed by deprotection of ester groups. All minor ingredients and by-products formed during the process were identified and further studied. The final product was obtained in high yield and its high enantiomeric purity (>99%) was confirmed by chiral capillary electrophoretic analysis using β-cyclodextrin as a chiral selector. Antiretroviral activity data of (R)-PMPDAP and its diverse prodrugs against HIV and FIV were investigated. Akin to (R)-PMPDAP, both prodrugs inhibit FIV replication in a selective manner. Compared to the parent molecule, the amidate prodrug was 10-fold less active against FIV in cell culture, whereas the alkoxyalkyl ester prodrug was 200-fold more potent in inhibiting FIV replication in vitro. 相似文献
93.
Vesna Selaković Snežana Rauš Balind Lidija Radenović Zlatko Prolić Branka Janać 《Cell biochemistry and biophysics》2013,66(3):513-521
The aim of study was to investigate the effects of extremely low frequency magnetic field (ELF-MF; 50 Hz; 0.1, 0.25 and 0.5 mT) on oxidative stress in the brain of 3- (adult) and 10-month-old (middle-aged) gerbils. Nitric oxide (NO) level, superoxide (O2 ?) production, superoxide dismutase (SOD) activity, and index of lipid peroxidation (ILP) were measured in the forebrain cortex, striatum, hippocampus, and cerebellum immediately and 3 days after cessation of 7-day exposure. In all gerbils, ELF-MF significantly increased oxidative stress in all tested brain regions. This effect was correlated with the value of magnetic induction and was higher in middle-aged gerbils. Three days after cessation of exposure, the values of examined parameters were closer to control levels. In adult gerbils, the effect of ELF-MF of 0.1 mT on NO level, O2 ? production and SOD activity was almost fully disappeared, and ILP was at the control level regardless of the value of magnetic induction. In middle-aged gerbils, the effect of ELF-MF was still present but to a lesser degree than those observed immediately after cessation of exposure. These findings pointed out the ability of ELF-MF to induce age- and magnetic induction-dependent modification of oxidative stress in the brain. 相似文献
94.
Petrin Z 《Oecologia》2011,167(2):513-524
Much recent ecological research has centred on the interrelations between species diversity and ecological processes. In the
present study, I show how species traits may aid in comprehending ecology by studying the link between an environmental variable
and functional traits. I examined the composition of species traits with a theoretically underpinned relationship to ecological
processes along a pH gradient. I focused on body size, reproductive output, life cycle length and feeding habit of mayflies
and stoneflies. In mayfly assemblages, I found smaller body size, greater reproductive output, faster life cycles and a larger
proportion of gathering collectors and scrapers with increasing pH. In stonefly assemblages, I found smaller body size, greater
reproductive output and faster life cycles at sites with a history of long-term natural acidification, but no clear trends
in feeding habits and in most traits where acidification is anthropogenic. The results suggest that mayflies and stoneflies
exhibit different ecological functions following different ecological strategies. Mayflies follow an opportunistic strategy
relative to stoneflies, likely facilitating high rates of ecological processes with respect to the autotrophic resource base
at neutral sites. Relative to mayflies, stoneflies follow an equilibrium strategy contributing to ecological functioning in
heterotrophic ecosystems and likely maintaining heterotrophic processes despite the erosion of species diversity in response
to acidification. The rules governing an ecological community may be more readily revealed by studying the distribution of
species traits instead of species diversity; by studying traits, we are likely to improve our understanding of the workings
of ecological communities. 相似文献
95.
Hayes TB Anderson LL Beasley VR de Solla SR Iguchi T Ingraham H Kestemont P Kniewald J Kniewald Z Langlois VS Luque EH McCoy KA Muñoz-de-Toro M Oka T Oliveira CA Orton F Ruby S Suzawa M Tavera-Mendoza LE Trudeau VL Victor-Costa AB Willingham E 《The Journal of steroid biochemistry and molecular biology》2011,127(1-2):64-73
Atrazine is the most commonly detected pesticide contaminant of ground water, surface water, and precipitation. Atrazine is also an endocrine disruptor that, among other effects, alters male reproductive tissues when animals are exposed during development. Here, we apply the nine so-called "Hill criteria" (Strength, Consistency, Specificity, Temporality, Biological Gradient, Plausibility, Coherence, Experiment, and Analogy) for establishing cause-effect relationships to examine the evidence for atrazine as an endocrine disruptor that demasculinizes and feminizes the gonads of male vertebrates. We present experimental evidence that the effects of atrazine on male development are consistent across all vertebrate classes examined and we present a state of the art summary of the mechanisms by which atrazine acts as an endocrine disruptor to produce these effects. Atrazine demasculinizes male gonads producing testicular lesions associated with reduced germ cell numbers in teleost fish, amphibians, reptiles, and mammals, and induces partial and/or complete feminization in fish, amphibians, and reptiles. These effects are strong (statistically significant), consistent across vertebrate classes, and specific. Reductions in androgen levels and the induction of estrogen synthesis - demonstrated in fish, amphibians, reptiles, and mammals - represent plausible and coherent mechanisms that explain these effects. Biological gradients are observed in several of the cited studies, although threshold doses and patterns vary among species. Given that the effects on the male gonads described in all of these experimental studies occurred only after atrazine exposure, temporality is also met here. Thus the case for atrazine as an endocrine disruptor that demasculinizes and feminizes male vertebrates meets all nine of the "Hill criteria". 相似文献
96.
97.
Kristen Feher Jan Lisec Lilla R?misch-Margl Joachim Selbig Alfons Gierl Hans-Peter Piepho Zoran Nikoloski Lothar Willmitzer 《PloS one》2014,9(1)
Heterosis, the greater vigor of hybrids compared to their parents, has been exploited in maize breeding for more than 100 years to produce ever better performing elite hybrids of increased yield. Despite extensive research, the underlying mechanisms shaping the extent of heterosis are not well understood, rendering the process of selecting an optimal set of parental lines tedious. This study is based on a dataset consisting of 112 metabolite levels in young roots of four parental maize inbred lines and their corresponding twelve hybrids, along with the roots'' biomass as a heterotic trait. Because the parental biomass is a poor predictor for hybrid biomass, we established a model framework to deduce the biomass of the hybrid from metabolite profiles of its parental lines. In the proposed framework, the hybrid metabolite levels are expressed relative to the parental levels by incorporating the standard concept of additivity/dominance, which we name the Combined Relative Level (CRL). Our modeling strategy includes a feature selection step on the parental levels which are demonstrated to be predictive of CRL across many hybrid metabolites. We demonstrate that these selected parental metabolites are further predictive of hybrid biomass. Our approach directly employs the diallel structure in a multivariate fashion, whereby we attempt to not only predict macroscopic phenotype (biomass), but also molecular phenotype (metabolite profiles). Therefore, our study provides the first steps for further investigations of the genetic determinants to metabolism and, ultimately, growth. Finally, our success on the small-scale experiments implies a valid strategy for large-scale experiments, where parental metabolite profiles may be used together with profiles of selected hybrids as a training set to predict biomass of all possible hybrids. 相似文献
98.
Zlatko Smole Nela Nikolic Fran Supek Tomislav ?muc Ivo F Sbalzarini Anita Krisko 《BMC evolutionary biology》2011,11(1):26
Background
Prokaryotic environmental adaptations occur at different levels within cells to ensure the preservation of genome integrity, proper protein folding and function as well as membrane fluidity. Although specific composition and structure of cellular components suitable for the variety of extreme conditions has already been postulated, a systematic study describing such adaptations has not yet been performed. We therefore explored whether the environmental niche of a prokaryote could be deduced from the sequence of its proteome. Finally, we aimed at finding the precise differences between proteome sequences of prokaryotes from different environments. 相似文献99.
Stephan Pabinger Robert Rader Rasmus Agren Jens Nielsen Zlatko Trajanoski 《BMC systems biology》2011,5(1):20
Background
Recent advances in genomic sequencing have enabled the use of genome sequencing in standard biological and biotechnological research projects. The challenge is how to integrate the large amount of data in order to gain novel biological insights. One way to leverage sequence data is to use genome-scale metabolic models. We have therefore designed and implemented a bioinformatics platform which supports the development of such metabolic models. 相似文献100.
Osorio S Alba R Nikoloski Z Kochevenko A Fernie AR Giovannoni JJ 《Plant physiology》2012,159(4):1713-1729