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1.
Cristian A. Acevedo Elizabeth Y. Sanchez Juan G. Reyes Manuel E. Young 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》2010,878(3-4):449-455
It is known that skin releases volatile organic compounds to the environment, and also that its emission pattern changes with aging of the skin. It could be considered, that these compounds are intermediaries in cell metabolism, since many intermediaries of metabolic pathways have a volatile potential. In this work, a simple and non-destructive method consisting of SPME sampling and GC/MS analysis was developed to identify volatile organic emanations from cell cultures. This technique, applied to skin cells culture, indicates that the cells or cell metabolism produce several skin emissions. Chemometric analysis was performed in order to explore the relationship between a volatile profile and the senescence of cell cultures. Volatile profiles were different for cell cultures in different degrees of senescence, indicating that volatile compound patterns could be used to provide information about the age of skin cells. 相似文献
2.
Tanner Miest Dyana Saenz Anne Meehan Manuel Llano Eric M. Poeschla 《Methods (San Diego, Calif.)》2009,47(4):298-303
RNAi is a powerful technology for analyzing gene function in human cells. However, its utility can be compromised by inadequate knockdown of the target mRNA or by interpretation of effects without rigorous controls. We review lentiviral vector-based methods that enable transient or stable knockdowns to trace mRNA levels in human CD4+ T cell lines and other targets. Critical controls are reviewed, including rescue of the pre-knockdown phenotype by re-expression of the targeted gene. The time from thinking about a potential knockdown target to analysis of phenotypes can be as short as a few weeks. 相似文献
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4.
W. Kelley Thomas J. T. Vida Linda M. Frisse Manuel Mundo James G. Baldwin 《Journal of nematology》1997,29(3):250-254
To effectively integrate DNA sequence analysis and classical nematode taxonomy, we must be able to obtain DNA sequences from formalin-fixed specimens. Microdissected sections of nematodes were removed from specimens fixed in formalin, using standard protocols and without destroying morphological features. The fixed sections provided sufficient template for multiple polymerase chain reaction-based DNA sequence analyses. 相似文献
5.
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
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R A Deems D Lombardo B P Morgan E D Mihelich E A Dennis 《Biochimica et biophysica acta》1987,917(2):258-268
Manoalide, a natural product from sponge, displays anti-inflammatory activity in vivo. Previous work has shown that manoalide is also a potent covalent inhibitor of the extracellular phospholipase A2 from cobra venom and that the inhibition correlated with a pH-dependent change in manoalide (Lombardo and Dennis (1985) J. Biol. Chem. 260, 7234-7240). Manoalide contains two rings and the opening of either would produce an alpha,beta-unsaturated aldehyde. The cobra venom phospholipase A2 may be able to catalyze the opening or isomerization of one of these rings, raising the possibility that manoalide is acting as a suicide substrate. To ascertain the role of the gamma-lactone ring in the inhibition, we have now investigated a synthetic manoalide analogue, 3(cis,cis-7,10)-hexadecadienyl-4-hydroxy-2-butenolide (HDHB) which contains only the alpha,beta-unsaturated gamma-lactone ring. We have found that the closed and open forms are in rapid equilibrium between pH 4 and 9 with the cyclic form being preferred at acidic pH values and the open cis form preferred at pH 9.5. When the pH is raised above 12, the alpha,beta double bond isomerizes to form trans-HDHB. Once the trans compound is formed, it is stable at all pH values and does not recyclize to the gamma-lactone ring. The observed pKa of 7.7 found for the inhibition of manoalide agrees well with the transition of the closed to the cis form of the gamma-lactone ring. Kinetic experiments with the HDHB compound show that under conditions in which the cis and closed form of the inhibitor are present in equal molar ratios, HDHB is not an irreversible inhibitor, but reversibly competes with substrate. However, the kinetics of this inhibition are complex and do not follow either pure competitive or non-competitive inhibition. The trans-HDHB exhibits similar complex kinetic but is several times more potent. The distinct differences between the behavior of manoalide and HDHB clearly indicate that while the gamma-lactone ring may play an important role in manoalide inhibition, it alone does not produce irreversible inhibition. 相似文献
8.
Luís M. S. Loura Fábio Fernandes Manuel Prieto 《European biophysics journal : EBJ》2010,39(4):589-607
Lateral membrane heterogeneity, in the form of lipid rafts and microdomains, is currently implicated in cell processes including signal transduction, endocytosis, and cholesterol trafficking. Various biophysical techniques have been used to detect and characterize lateral membrane domains. Among these, Förster resonance energy transfer (FRET) has the crucial advantage of being sensitive to domain sizes smaller than 50-100 nm, below the resolution of optical microscopy but, apparently, similar to those of rafts in cell membranes. In the last decade, several formalisms for the analysis of FRET in heterogeneous membrane systems have been derived and applied to the study of microdomains. They are critically described and illustrated here. 相似文献
9.
Paleoecology allows construction of paleoenvironmental models, faunal changes and evolutionary trends of paleontological taxa using modern analogs. However, when linking modern analogs to paleontological taxa in paleoecological reconstruction, differential taxonomic preservation in the fossil record has to be taken into account. Paleontologists have known the biased nature of the fossil record since Efremov’s publication on taphonomy in 1940, yet many ecological models of habitats associated with hominins in paleontological and archaeological sites in Africa and elsewhere barely address the complexity of the fossil record. We use randomly sampled ungulates from modern biomes in a comparative taxonomic abundance to demonstrate how the combination of modern thanatocoenoses and taphocoenoses, when used in reference to habitat-specific biocoenosis, produce better inferences of past habitats in paleontological and archaeological sites than approaches currently used. 相似文献
10.
The application of multi-objective optimisation to evolutionary robotics is receiving increasing attention. A survey of the literature reveals the different possibilities it offers to improve the automatic design of efficient and adaptive robotic systems, and points to the successful demonstrations available for both task-specific and task-agnostic approaches (i.e., with or without reference to the specific design problem to be tackled). However, the advantages of multi-objective approaches over single-objective ones have not been clearly spelled out and experimentally demonstrated. This paper fills this gap for task-specific approaches: starting from well-known results in multi-objective optimisation, we discuss how to tackle commonly recognised problems in evolutionary robotics. In particular, we show that multi-objective optimisation (i) allows evolving a more varied set of behaviours by exploring multiple trade-offs of the objectives to optimise, (ii) supports the evolution of the desired behaviour through the introduction of objectives as proxies, (iii) avoids the premature convergence to local optima possibly introduced by multi-component fitness functions, and (iv) solves the bootstrap problem exploiting ancillary objectives to guide evolution in the early phases. We present an experimental demonstration of these benefits in three different case studies: maze navigation in a single robot domain, flocking in a swarm robotics context, and a strictly collaborative task in collective robotics. 相似文献