Molecule modeling of human pentameric alpha(7) neuronal nicotinic acetylcholine receptor and its interaction with its agonist and competitive antagonist

The nicotinic Acetylcholine Receptor (nAChR) is the major class of neurotransmitter receptors that is involved in many neurodegenerative conditions such as schizophrenia, Alzheimer's and Parkinson's diseases. The N-terminal region or Ligand Binding Domain (LBD) of nAChR is located at pre- and post-synaptic nervous system, which mediates synaptic transmission. nAChR acts as the drug target for agonist and competitive antagonist molecules that modulate signal transmission at the nerve terminals. Based on Acetylcholine Binding Protein (AChBP) from Lymnea stagnalis as the structural template, the homology modeling approach was carried out to build three dimensional model of the N-terminal region of human alpha(7)nAChR. This theoretical model is an assembly of five alpha(7) subunits with 5 fold axis symmetry, constituting a channel, with the binding picket present at the interface region of the subunits. alpha-netlrotoxin is a potent nAChR competitive antagonist that readily blocks the channel resulting in paralysis. The molecular interaction of alpha-Bungarotoxin, a long chain alpha-neurotoxin from (Bungarus multicinctus) and human alpha(7)nAChR seas studied. Agonists such as acetylcholine, nicotine, which are used in it diverse array of biological activities, such as enhancements of cognitive performances, were also docked with the theoretical model of human alpha(7)nAChR. These docked complexes were analyzed further for identifying the crucial residues involved in interaction. These results provide the details of interaction of agonists and competitive antagonists with three dimensional model of the N-terminal region of human alpha(7)nAChR and thereby point to the design of novel lead compounds.

The influence of winter oilseed rape (Brassica napus ssp. oleifera var. biennis) cultivar and grass genotype on the competitive balance between crop and grass weeds

Four experiments conducted over three seasons (2002–05) at the Crops Research Unit, University of Reading, investigated effects of canopy management of autumn sown oilseed rape (Brassica napus L. ssp. oleifera var. biennis (DC.) Metzg.) on competition with grass weeds. Emphasis was placed on the effect of the crop on the weeds. Rape canopy size was manipulated using sowing date, seed rate and the application of autumn fertilizer. Lolium multiflorum Lam., L.rboucheanum Kunth and Alopecurus myosuroides Huds. were sown as indicative grass weeds. The effects of sowing date, seed rate and autumn nitrogen on crop competitive ability were correlated with rape biomass and fractional interception of photosynthetically active radiation (PAR) by the rape floral layer, to the extent that by spring there was good evidence of crop: weed replacement. An increase in seed rate up to the highest plant densities tested increased both rape biomass and competitiveness, e.g. in 2002/3, L. multiflorum head density was reduced from 539 to 245 heads/m2 and spikelet density from 13 170 to 5960 spikelets/m2 when rape plant density was increased from 16 to 81 plants/m2. Spikelets/head of Lolium spp. was little affected by rape seed rate, but the length of heads of A. myosuroides was reduced by 9%when plant density was increased from 29–51 plants/m2. Autumn nitrogen increased rape biomass and reduced L. multiflorum head density (415 and 336 heads/m2 without and with autumn nitrogen, respectively) and spikelet density (9990 and 8220 spikelets/m2 without and with autumn nitrogen, respectively). The number of spikelets/head was not significantly affected by autumn nitrogen. Early sowing could increase biomass and competitiveness, but poor crop establishment sometimes overrode the effect. Where crop and weed establishment was similar for both sowing dates, a 2-week delay (i.e. early September to mid-September) increased L. multiflorum head density from 226 to 633 heads/m2 and spikelet density from 5780 to 15 060 spikelets/m2.

The influence of winter oilseed rape (Brassica napus ssp oleifera var. biennis) cultivar and grass genotype on the competitive balance between crop and grass weeds

Three experiments conducted over two years (2002-04) at the Crops Research Unit, University of Reading, investigated competition between autumn sown oilseed rape cultivars (Brassica napus L. ssp. oleifera var. biennis (DC.) Metzg.) and Lolium multiflorum Lam., L. x boucheanum Kunth and Alopecurus myosuroides Huds., sown as indicative grass weeds. Rape cultivar (cv.) had a substantial effect on grass weed seed return. Over the six cultivars tested, L. multiflorum spikelet production ranged from just under 400 spikelets/m(2) in the presence of cv. Winner to nearly 5800 in competition with cv. Lutin. Cultivar competitiveness was associated with high biomass, large dense floral layers and early stem extension. There was some evidence of differential competitive tolerance between rape cultivars. The results suggested that rape cultivars could be screened for competitiveness by measuring floral layer interception of photosynthetic active radiation. L. x boucheanum cultivars varied in ability to compete with rape. In the absence of inter-specific competition, spikelet density was similar for Aberecho and Polly (circa 31000 spikelets/m(2)) but when grown with rape Polly outyielded Aberecho (i.e. 12 090 and 7990 spikelets/m(2) respectively).

Detection and enumeration of sulphate-reducing bacteria in estuarine sediments by competitive PCR

The distribution of sulphate-reducing bacteria (SRB) in the sediments of the Colne River estuary, Essex, UK covering different saline concentrations of sediment porewater was investigated by the use of quantitative competitive PCR. Here, we show that a new PCR primer set and a new quantitative method using PCR are useful tools for the detection and the enumeration of SRB in natural environments. A PCR primer set selective for the dissimilatory sulphite reductase gene (dsr) of SRB was designed. PCR amplification using the single set of dsr-specific primers resulted in PCR products of the expected size from all 27 SRB strains tested, including Gram-negative and positive species. Sixty clones derived from sediment DNA using the primers were sequenced and all were closely related with the predicted dsr of SRB. These results indicate that PCR using the newly designed primer set are useful for the selective detection of SRB from a natural sample. This primer set was used to estimate cell numbers by dsr selective competitive PCR using a competitor, which was about 20% shorter than the targeted region of dsr. This procedure was applied to sediment samples from the River Colne estuary, Essex, UK together with simultaneous measurement of in situ rates of sulphate reduction. High densities of SRB ranging from 0.2 - 5.7 × 108 cells ml-1 wet sediment were estimated by the competitive PCR assuming that all SRB have a single copy of dsr. Using these estimates cell specific sulphate reduction rates of 10-17 to 10-15 mol of SO42- cell-1 day-1 were calculated, which is within the range of, or lower than, those previously reported for pure cultures of SRB. Our results show that the newly developed competitive PCR technique targeted to dsr is a powerful tool for rapid and reproducible estimation of SRB numbers in situ and is superior to the use of culture-dependent techniques.

Use of 16S rRNA-targeted oligonucleotide probes to investigate function and phylogeny of sulphate-reducing bacteria and methanogenic archaea in a UK estuary

Sulphate-reducing bacteria (SRB) and methanogenic archaea (MA) are important anaerobic terminal oxidisers of organic matter. However, we have little knowledge about the distribution and types of SRB and MA in the environment or the functional role they play in situ. Here we have utilised sediment slurry microcosms amended with ecologically significant substrates, including acetate and hydrogen, and specific functional inhibitors, to identify the important SRB and MA groups in two contrasting sites on a UK estuary. Substrate and inhibitor additions had significant effects on methane production and on acetate and sulphate consumption in the slurries. By using specific 16S-targeted oligonucleotide probes we were able to link specific SRB and MA groups to the use of the added substrates. Acetate consumption in the freshwater-dominated sediments was mediated by Methanosarcinales under low-sulphate conditions and Desulfobacter under the high-sulphate conditions that simulated a tidal incursion. In the marine-dominated sediments, acetate consumption was linked to Desulfobacter. Addition of trimethylamine, a non-competitive substrate for methanogenesis, led to a large increase in Methanosarcinales signal in marine slurries. Desulfobulbus was linked to non-sulphate-dependent H-2 consumption in the freshwater sediments. The addition of sulphate to freshwater sediments inhibited methane production and reduced signal from probes targeted to Methanosarcinales and Methanomicrobiales, while the addition of molybdate to marine sediments inhibited Desulfobulbus and Desulfobacterium. These data complement our understanding of the ecophysiology of the organisms detected and make a firm connection between the capabilities of species, as observed in the laboratory, to their roles in the environment. (C) 2003 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.

Competitive strategy revisited: contested concepts and dynamic capabilities

Strategy is a contested concept. The generic literature is characterized by a diverse range of competing theories and alternative perspectives. Traditional models of the competitive strategy of construction firms have tended to focus on exogenous factors. In contrast, the resource-based view of strategic management emphasizes the importance of endogenous factors. The more recently espoused concept of dynamic capabilities extends consideration beyond static resources to focus on the ability of firms to reconfigure their operating routines to enable responses to changing environments. The relevance of the dynamics capabilities framework to the construction sector is investigated through an exploratory case study of a regional contractor. The focus on how firms continuously adapt to changing environments provides new insights into competitive strategy in the construction sector. Strong support is found for the importance of path dependency in shaping strategic choice. The case study further suggests that strategy is a collective endeavour enacted by a loosely defined group of individual actors. Dynamic capabilities are characterized by an empirical elusiveness and as such are best construed as situated practices embedded within a social and physical context.

The competitive dialogue procedure: Advantages, disadvantages, and its implementation into English and Dutch law

Competitive Dialogue (CD) is a new contract award procedure of the European Community (EC). It is set out in Article 29 of the 'Public Sector Directive' 2004/18/EC. Over the last decades, projects were becoming more and more complex, and the existing EC procedures were no longer suitable to procure those projects. The call for a new procedure resulted in CD. This paper describes how the Directive has been implemented into the laws of two member states: the UK and the Netherlands. In order to implement the Directive, both lawmakers have set up a new and distinct piece of legislation. In each case, large parts of the Directive’s content have been repeated ‘word for word’; only minor parts have been reworded and/or restructured. In the next part of the paper, the CD procedure is examined in different respects. First, an overview is given on the different EC contract award procedures (open, restricted, negotiated, CD) and awarding methods (lowest price and Most Economically Advantageous Tender, MEAT). Second, the applicability of CD is described: Among other limitations, CD can only be applied to public contracts for works, supplies, and services, and this scope of application is further restricted by the exclusion of certain contract types. One such exclusion concerns services concessions. This means that PPP contracts which are set up as services concessions cannot be awarded by CD. The last two parts of the paper pertain to the main features of the CD procedure – from ‘contract notice’ to ‘contract award’ – and the advantages and disadvantages of the procedure. One advantage is that the dialogue allows the complexity of the project to be disentangled and clarified. Other advantages are the stimulation of innovation and creativity. These advantages are set against the procedure’s disadvantages, which include high transaction costs and a perceived hindrance of innovation (due to an ambiguity between transparency and fair competition). It is concluded that all advantages and disadvantages are related to one of three elements: communication, competition, and/or structure of the procedure. Further research is needed to find out how these elements are related.

Enacting competitiveness: an empirical investigation

The paper draws from three case studies of regional construction firms operating in the UK. The case studies provide new insights into the ways in which such firms strive to remain competitive. Empirical data was derived from multiple interactions with senior personnel from with each firm. Data collection methods included semi-structured interviews, informal interactions, archival research, and workshops. The initial research question was informed by existing resource-based theories of competitiveness and an extensive review of constructionspecific literature. However, subsequent emergent empirical findings progressively pointed towards the need to mobilise alternative theoretical models that emphasise localised learning and embeddedness. The findings point towards the importance of de-centralised structures that enable multiple business units to become embedded within localised markets. A significant degree of autonomy is essential to facilitate entrepreneurial behaviour. In essence, sustained competitiveness was found to rest on the way de-centralised business units enact ongoing processes of localised learning. Once local business units have become embedded within localised markets, the essential challenge is how to encourage continued entrepreneurial behaviour while maintaining some degree of centralised control and coordination. This presents a number of tensions and challenges which play out differently across each of the three case studies.

Partnering in flight: From being to becoming

Current literature offers little understanding about how procurement methods are enacted in practice. Developments in procurement are often viewed as the result of responding to recommendations from particular constituents within the sector. The research seeks to remove itself from such deterministic leaning, counselling instead that procurement should not be viewed in static terms, but dynamically manifesting over time within a complex web of interconnections between various actors, their situated context and the broader industrial structure. Attention is given to how a client and construction firm engaged in a collusive interaction to realise an innovative procurement method that derived its legitimacy from a backcloth of initiatives promoted by various commentators. A case study of a medium-size regional contractor demonstrates how the first partnering arrangement was enacted within the UK affordable housing maintenance sector in the UK. The case study finds that the enactment of new procurement methods strongly relies on iterative learning between clients and contractors. It is further suggested that construction firms need to initiate new procurement in order to remain competitive within the sector. The findings point towards a pro-active initiative by the contractor and client to enact a ‘procurement first’. Encouragement may be drawn from this example by other contractors seeking to offer more than simply responsive procurement solutions.

Mathematical modelling of competitive LDL/VLDL binding and uptake by hepatocytes

Elevated levels of low-density-lipoprotein cholesterol (LDL-C) in the plasma are a well-established risk factor for the development of coronary heart disease. Plasma LDL-C levels are in part determined by the rate at which LDL particles are removed from the bloodstream by hepatic uptake. The uptake of LDL by mammalian liver cells occurs mainly via receptor-mediated endocytosis, a process which entails the binding of these particles to specific receptors in specialised areas of the cell surface, the subsequent internalization of the receptor-lipoprotein complex, and ultimately the degradation and release of the ingested lipoproteins' constituent parts. We formulate a mathematical model to study the binding and internalization (endocytosis) of LDL and VLDL particles by hepatocytes in culture. The system of ordinary differential equations, which includes a cholesterol-dependent pit production term representing feedback regulation of surface receptors in response to intracellular cholesterol levels, is analysed using numerical simulations and steady-state analysis. Our numerical results show good agreement with in vitro experimental data describing LDL uptake by cultured hepatocytes following delivery of a single bolus of lipoprotein. Our model is adapted in order to reflect the in vivo situation, in which lipoproteins are continuously delivered to the hepatocyte. In this case, our model suggests that the competition between the LDL and VLDL particles for binding to the pits on the cell surface affects the intracellular cholesterol concentration. In particular, we predict that when there is continuous delivery of low levels of lipoproteins to the cell surface, more VLDL than LDL occupies the pit, since VLDL are better competitors for receptor binding. VLDL have a cholesterol content comparable to LDL particles; however, due to the larger size of VLDL, one pit-bound VLDL particle blocks binding of several LDLs, and there is a resultant drop in the intracellular cholesterol level. When there is continuous delivery of lipoprotein at high levels to the hepatocytes, VLDL particles still out-compete LDL particles for receptor binding, and consequently more VLDL than LDL particles occupy the pit. Although the maximum intracellular cholesterol level is similar for high and low levels of lipoprotein delivery, the maximum is reached more rapidly when the lipoprotein delivery rates are high. The implications of these results for the design of in vitro experiments is discussed.