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1.
Neuronal cell responses and interactions with the epithelial and fibroblastic cells of the skin are a key factor in the production in vivo of the irritation/inflammatory response. Currently, few in vitro models are available that contain dermal, epidermal and the relevant neuronal components. The primary objective of this study was to produce and maintain a 3-D in vitro model of human skin containing these elements. The relevant neuronal component was supplied by adding sensory neurons derived from the dorsal root ganglion (DRG). Since adult neuronal cells do not grow significantly in vivo or in vitro, and since it is very difficult to obtain such cells from humans, it was necessary to employ embryonic rat DRG cells. The ultimate purpose of this model is to improve prediction of the in vivo skin irritancy potential of chemicals and formulations, without the need to use animal models. In addition, this approach has also been applied to the in vitro human eye and bronchial 3-D models being developed in the FRAME Alternatives Laboratory.  相似文献   
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Abstract

Ethyl dialkylphosphonoacetates were prepared from the corresponding dimethylalkylphosphites via the Arbuzov reaction with ethyl bromoacetate. The phosphonoacetates so produced were converted into enaminoacetates by reaction with DMF dimethylacetal and these were used as bidentate electrophiles for the synthesis of phosphonopyrimidones. Several of these compounds were tested for biological activity but none were found to possess antiviral activity.  相似文献   
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System A and N amino acid transporters are key effectors of movement of amino acids across the plasma membrane of mammalian cells. These Na+-dependent transporters of the SLC38 gene family are highly sensitive to changes in pH within the physiological range, with transport markedly depressed at pH 7.0. We have investigated the possible role of histidine residues in the transporter proteins in determining this pH-sensitivity. The histidine-modifying agent DEPC (diethyl pyrocarbonate) markedly reduces the pH-sensitivity of SNAT2 and SNAT5 transporters (representative isoforms of System A and N respectively, overexpressed in Xenopus oocytes) in a concentration-dependent manner but does not completely inactivate transport activity. These effects of DEPC were reversed by hydroxylamine and partially blocked in the presence of excess amino acid substrate. DEPC treatment also blocked a reduction in apparent affinity for Na+ (K0.5Na+) of the SNAT2 transporter at low external pH. Mutation of the highly conserved C-terminal histidine residue to alanine in either SNAT2 (H504A) or SNAT5 (H471A) produced a transport phenotype exhibiting reduced, DEPC-resistant pH-sensitivity with no change in K0.5Na+ at low external pH. We suggest that the pH-sensitivity of these structurally related transporters results at least partly from a common allosteric mechanism influencing Na+ binding, which involves an H+-modifier site associated with C-terminal histidine residues.  相似文献   
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With more than 160 years of contrasting fertilizer regimes, the Broadbalk winter wheat experiment represents a unique experimental resource for studying the effects of long-term fertilizer application on microbial population diversity. Using DGGE and clone library analysis, we report here on eubacterial species diversity (16S rRNA gene) and diversity within two sets of gene products associated with microbial N acquisition: NifH (nitrogen fixation) and AmtB (ammonium transport). Comparisons were made within and between soils treated with mineral N fertilizer, farmyard manure or receiving no fertilizer. Analysis of 16S rRNA gene DGGE profiles showed no clear patterns to qualitatively distinguish bacterial community structure between the three different treatments (P > 0.05), with all samples containing a range of eubacterial taxa similar to those that are characteristic of soil bacteria reported elsewhere. Intra-plot heterogeneity was high and of a similar magnitude to that between treatments. This lack of qualitative between plot differences was echoed in the representative sequences of 16S rRNA, nifH, and amtB genes in the various samples. Taken together, both phylogenetic and functional gene analyses showed bacterial communities in the Broadbalk-trial soil were very stable and relatively non-responsive to long-term management of balanced fertilizer inputs.  相似文献   
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Background  

Organisms are capable of developing different phenotypes by altering the genes they express. This phenotypic plasticity provides a means for species to respond effectively to environmental conditions. One of the most dramatic examples of phenotypic plasticity occurs in the highly social hymenopteran insects (ants, social bees, and social wasps), where distinct castes and sexes all arise from the same genes. To elucidate how variation in patterns of gene expression affects phenotypic variation, we conducted a study to simultaneously address the influence of developmental stage, sex, and caste on patterns of gene expression in Vespula wasps. Furthermore, we compared the patterns found in this species to those found in other taxa in order to investigate how variation in gene expression leads to phenotypic evolution.  相似文献   
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An increase in public transport use has the potential to contribute to improving population health, and there is growing interest in innovative public transport systems. Yet how new public transport infrastructure is experienced and integrated (or not) into daily practice is little understood. We investigated how the Cambridgeshire Guided Busway, UK, was used and experienced in the weeks following its opening, using the method of participant observation (travelling on the busway and observing and talking to passengers) and drawing on Normalization Process Theory to interpret our data. Using excerpts of field notes to support our interpretations, we describe how the ease with which the new transport system could be integrated into existing daily routines was important in determining whether individuals would continue to use it. It emerged that there were two groups of passengers with different experiences and attitudes. Passengers who had previously travelled frequently on regular bus services did not perceive the new system to be an improvement; consequently, they were frustrated that it was differentiated from and not coherent with the regular system. In contrast, passengers who had previously travelled almost exclusively by car appraised the busway positively and perceived it to be a novel and superior form of travel. Our rich qualitative account highlights the varied and creative ways in which people learn to use new public transport and integrate it into their everyday lives. This has consequences for the introduction and promotion of future transport innovations. It is important to emphasise the novelty of new public transport, but also the ways in which its use can become ordinary and routine. Addressing these issues could help to promote uptake of other public transport interventions, which may contribute to increasing physical activity and improving population health.  相似文献   
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