The biochemical role of the small G protein Rac1 in cell signalling pathways - Interaction with RhoGDI and the phagocyte NADPH oxidase component, p67phox

Rac is a small G protein with a number of signalling roles. Along with other members of the Rho family of small GTPases, it is involved in the control of the actin cytoskeleton (Hall, 1992) and an apparently separate role in the activation of the NADPH oxidase, an enzymatic mechanism in phagocytes which forms superoxide in response to bacterial infection. In an inactive state, Rho family proteins exist in a complex with a second cytosolic protein, Rho guanine nucleotide dissociation inhibitor, RhoGDI. Activation causes dissociation of the Rac GDI complex and movement of Rac to the membrane. Spectroscopic studies have been used to investigate the interaction of Racl with other molecules, such as p67phox, a component of the NADPH oxidase complex. Complexes of racl with 2'(3')O-(N-methylanthraniloyl) (mant) fluorescent nucleotide analogues (eg. mantGDP) have been used to try to develop methods to study the interaction of Racl and p67phox. Although a previous report indicates a fluorescent change when Racl (complexed to a fluorescent nucleotide analogue) is incubated with p67phox, these experiments could not be repeated. A number of other approaches have been taken to develop a system to monitor the interaction of Rac and p67phox. Fluorescent approaches have also been developed to study the interaction of Rac and RhoGDI. GDI has previously been labelled with the fluorophore N-[2-1-(maleimidyl)ethyl]-7- (diethylamino)coumarin-3-carboxamide (MDCC) on a single cysteine in our laboratory and shows a large fluorescence decrease on Rac binding. Rac requires a lipid modification at the C-terminus to interact with RhoGDI, which presents a number of experimental difficulties. A system has been developed using C-terminally truncated (E.coli expressed) Rac and a farnesylated C-terminal peptide that mimics full length Racl that has been lipid modified in vivo (Newcombe et al., 1999). We are currently using this system to study the interaction of Racl with GDI and a number Racl point mutants have been made in the major regions of divergence between Ras superfamily proteins, based on the crystal structure of Racl (Hirshberg et al., 1997). In addition, a Racl/H-Ras chimaeric protein has been made and expressed in this laboratory. Results indicate that a region of the Racl effector loop is important for the Racl GDI interaction, with mutations in the insertion loop of Racl having little or no affect on the affinity of the Racl GDI interaction (Newcombe, Hunter & Webb, unpublished results). In addition, the interaction of Racl with a number of novel fluorescent nucleotide analogues including 3'-O-[N-[2-(7-diethylaminocoumarin-3-carboxamido)ethyl]carbamoyl] GTP (cou-edaGTP) and coumarin343-edaGTP (but-edaGTP) have been tested, and Racl complexes have shown that the rate of nucleotide hydrolysis and exchange by Racl shows them to be good analogues of GTP. It is hoped that these analogues will be useful to study the interaction of Racl with other proteins, such as GDI and p67phox

Rapid solutions for application specific IGBT module design

The electric car, the all electric aircraft and requirements for renewable energy are prime examples of potential technologies needing to be addressed in the world problem of global warming/carbon emission etc. Power electronics are fundamental for the underpinning of these technologies and with the diverse requirements for electrical configurations and the range of environmental conditions, time to market is paramount for module manufacturers and systems designers alike. This paper presents a 'virtual' design methodology together with theoretical and experimental results that demonstrate enhanced product design with improved reliability, performance and cost value within competitive schemes

Future of the Virginia Oyster Industry

CHESAPEAKE BAY has long been famous for its oysters. Shared by Maryland and Virginia, this natural resource contributes greatly to the economic life of about thirty Tidewater counties. Virginia oyster grounds extend approximately half way up the bay and reach far up the numerous tributaries. In addition, there are thousands of acres of oyster grounds on the Sea Side of the Eastern Shore. Despite the magnitude of the acreage adapted for growing oysters, comparatively little effort has been made to find out just how valuable the industry is to the state or to explore its possibilities for development. Federal statistics indicate that Virginia ranks as the No. 1 oyster-producing state, the yield amounting to at least 5,000,000 bushels annually. Still, it is recognized that the state\u27s oyster grounds are capable of a much higher level of production than is witnessed toda

The nature of ecstasy-group related deficits in associative learning

Rationale/objectives: Research has revealed associative learning deficits among users of ecstasy; the present study explored the component processes underlying these deficits. Methods: Thirty-five ecstasy users and 62 non-ecstasy users completed a computer-based, verbal paired-associates learning task. Participants attempted to learn eight sequentially presented word pairs. After all eight had been presented, the first member of each pair was displayed and participants attempted to recall the second. Eight trials were administered. Correct responses on each trial, forgetting at various levels of learning, perseveration errors and the rate at which the associations were learned (trials to completion) were all recorded. Results: MANOVA revealed that ecstasy users performed worse overall and subsequent ANOVAs showed that users performed significantly worse on virtually all measures. Regression analysis revealed that over half of the ecstasy-group related variance in trials to completion was attributable to group differences in initial learning and forgetting. In relation to forgetting, it appears that cannabis use may be an important determinant. In relation to rate of learning (trials to completion) and initial learning, both ecstasy and cannabis may be implicated. Conclusions: There appears to be abundant evidence of associative learning deficits among ecstasy users. However, it appears that a range of illicit drugs including cannabis and ecstasy may contribute to these deficits

Elastic cavitation, tube hollowing, and differential growth in plants and biological tissues

Elastic cavitation is a well-known physical process by which elastic materials under stress can open cavities. Usually, cavitation is induced by applied loads on the elastic body. However, growing materials may generate stresses in the absence of applied loads and could induce cavity opening. Here, we demonstrate the possibility of spontaneous growth-induced cavitation in elastic materials and consider the implications of this phenomenon to biological tissues and in particular to the problem of schizogenous aerenchyma formation

Learning across business sectors: knowledge sharing between aerospace and construction

This report addresses the extent that managerial practices can be shared between the aerospace and construction sectors. Current recipes for learning from other industries tend to be oversimplistic and often fail to recognise the embedded and contextual nature of managerial knowledge. Knowledge sharing between business sectors is best understood as an essential source of innovation. The process of comparison challenges assumptions and better equips managers to cope with future change. Comparisons between the aerospace and construction sectors are especially useful because they are so different. The two sectors differ hugely in terms of their institutional context, structure and technological intensity. The aerospace sector has experienced extensive consolidation and is dominated by a small number of global companies. Aerospace companies operate within complex networks of global interdependency such that collaborative working is a commercial imperative. In contrast, the construction sector remains highly fragmented and is characterised by a continued reliance on small firms. The vast majority of construction firms compete within localised markets that are too often characterised by opportunistic behaviour. Comparing construction to aerospace highlights the unique characteristics of both sectors and helps explain how managerial practices are mediated by context. Detailed comparisons between the two sectors are made in a range of areas and guidance is provided for the implementation of knowledge sharing strategies within and across organisations. The commonly accepted notion of ‘best practice’ is exposed as a myth. Indeed, universal models of best practice can be detrimental to performance by deflecting from the need to adapt continuously to changing circumstances. Competitiveness in the construction sector too often rests on efficiency in managing contracts, with a particular emphasis on the allocation of risk. Innovation in construction tends to be problem-driven and is rarely shared from project to project. In aerospace, the dominant model of competitiveness means that firms have little choice other than to invest in continuous innovation, despite difficult trading conditions. Research and development (R&D) expenditure in aerospace continues to rise as a percentage of turnovers. A sustained capacity for innovation within the aerospace sector depends crucially upon stability and continuity of work. In the construction sector, the emergence of the ‘hollowed-out’ firm has undermined the industry’s capacity for innovation. Integrated procurement contexts such as prime contracting in construction potentially provide a more supportive climate for an innovation-based model of competitiveness. However, investment in new ways of working depends upon a shift in thinking not only amongst construction contractors, but also amongst the industry’s major clients

Ultraviolet-Resistant Bacterial Spores

A document summarizes a study in which it was found that spores of the SAFR-032 strain of Bacillus pumilus can survive doses of ultraviolet (UV) radiation, radiation, and hydrogen peroxide in proportions much greater than those of other bacteria. The study was part of a continuing effort to understand the survivability of bacteria under harsh conditions and develop means of sterilizing spacecraft to prevent biocontamination of Mars that could interfere with the search for life there

A simple graphical way of evaluating coverage and directional non-coverages

Evaluation of the coverage probability and, more recently, of the intervalar location of con dence intervals, is a useful procedure if exact and asymptotic methods for constructing con dence intervals are used for some populacional parameter. In this paper, a simple graphical procedure is presented to execute this kind of evaluation in con dence methods for linear combinations of k independent binomial proportions. Our proposal is based on the representation of the mesial and distal non-coverage probabilities on a plane. We carry out a simulation study to show how this graphical representation can be interpreted and used as a basis for the evaluation of intervalar location of con dence interval methods