A clonal culture system demonstrates that IL-4 induces a subpopulation of noncytolytic T cells with low CD8, perforin, and granzyme expression

Immune deviation of cytolytic T cell function, induced by type 2 cytokines like IL-4, is an attractive concept to explain failure of the immune system in some diseases. However, this concept is challenged by previous conflicting results on whether type 2 cytokine-producing CD8(+) T cells are cytolytic. Therefore, we have analyzed the relationship between cytolytic activity and cytokine production among large numbers of primary CD8(+) T cell clones. Single murine CD8(+) T cells of naive phenotype were activated at high efficiency with immobilized Abs to CD3, CD8, and CD11a in the presence of IL-2 (neutral conditions) or IL-2, IL-4, and anti-IFN-gamma Ab (type 2-polarizing conditions) for 8-9 days. Under neutral conditions, most clones produced IFN-gamma without IL-4 and were cytolytic. Under type 2-polarizing conditions, most clones produced IFN-gamma and IL-4 but displayed variable cytolytic activity and CD8 expression. Separation on the basis of surface CD8 levels revealed that, compared with CD8(high) cells from the same cultures, CD8(low) cells were poorly cytolytic and expressed low levels of perforin mRNA and protein and granzyme A, B, and C mRNA. A similar, smaller population of noncytolytic CD8(low) cells was identified among CD8(low) T cells activated in mixed lymphocyte reaction with IL-4. Variable efficiency of generation of the noncytolytic cells may account for the differing results of earlier studies. We conclude that IL-4 promotes the development of a noncytolytic CD8(low) T cell phenotype that might be important in tumor- or pathogen-induced immune deviation.

Economic and environmental impacts of pollution control in a system of environment and economic interdependence

The importance of the rate of change of the pollution stock in determining the damage to the environment has been an issue of increasing concern in the literature. This paper uses a three-sector (economy, population and environment), non-linear, discrete time, calibrated model to examine pollution control. The model explicitly links economic growth to the health of the environment. The stock of natural resources is affected by the rate of pollution flows, through their impact on the regenerative capacity of the natural resource stock. This can shed useful insights into pollution control strategies, particularly in developing countries where environmental resources are crucial for production in many sectors of the economy. Simulation exercises suggested that, under plausible assumptions, it is possible to reverse undesirable transient dynamics through pollution control expenditure, but this is dependent upon the strategies used for control. The best strategy is to spend money fostering the development of production technologies that reduce pollution rather than spending money dealing with the effects of the pollution flow into the environment. (C) 2001 Elsevier Science Ltd. All rights reserved.

An investigation into the interference rejection capability of a linear array in a wireless communications system

The suitable use of an array antenna at the base station of a wireless communications system can result in improvement in the signal-to-interference ratio (SIR). In general, the SIR is a function of the direction of arrival of the desired signal and depends on the configuration of the array, the number of elements, and their spacing. In this paper, we consider a uniform linear array antenna and study the effect of varying the number of its elements and inter-element spacing on the SIR performance. (C) 2002 Wiley Periodicals, Inc.

Cleaning symbioses from the parasites' perspective

Cleaning behaviour has generally been viewed from the cleaner or client's point of view. Few studies, however, have examined cleaning behaviour from the parasites' perspective, yet they are the equally-important third players in such associations. All three players are likely to have had their evolution affected by the association. As cleaner organisms are important predators of parasites, cleaners are likely to have an important effect on their prey. Little, however, is known of how parasites are affected by cleaning associations and the strategies that parasites use in response to cleaners. I examine here what parasites are involved in cleaning interactions, the effect cleaners have on parasites, the potential counter-adaptations that parasites have evolved against the predatory activities of cleaner organisms, the potential influence of cleaners on the life history traits of parasites, and other factors affected by cleaners. I have found that a wide range of ectoparasites from diverse habitats have been reported to interact with a wide range of cleaner organisms. Some of the life history traits of parasites are consistent with the idea that they are in response to cleaner predation. It is clear, however, that although many cleaning systems exist their ecological role is largely unexplored. This has likely been hindered by our lack of information on the parasites involved in cleaning interactions.

Optimising cleaning behaviour: minimising the costs and maximising ectoparasite removal

Little is known of how client fish minimise the costs of cleaning behaviour while maximising ectoparasite removal by cleaner fish. Previous studies have found that abundance on fish and infestation behaviour of gnathiid isopods, the main parasite eaten by cleaner fish, varies diurnally. We examined whether reduced foraging is a cost of cleaning behaviour in clients and whether the behaviour of the client fish, the thick-lipped wrasse Hemigymnus melapterus, towards the cleaner fish Labroides dimidiatus varied diurnally to maximise ectoparasite removal, possibly in response to the diurnal changes in the abundance and infestation patterns of gnathiids. We found that during the midday and afternoon, client foraging rates were negatively related to the duration and frequency of inspections, suggesting that cleaning may, at some times of the day, be energetically costly to the client in terms of reduced foraging opportunities. Surprisingly, we found that the duration and frequency of inspections of clients by cleaners did not vary among diel time periods. A model of gnathiid dynamics on individual fish is proposed. It shows that the observed diurnal pattern in gnathiid abundance on fish can be generated with the constant duration and frequency of inspections that was observed in this study. Thus clients would not have more gnathiids removed by modifying their cleaning behaviour.

Inducible system in human hepatoma cell lines for hepatitis C virus production

We cloned the complete complementary DNA of an isolate of the hepatitis C virus, HCV-S1, into a tetra cycline-inducible expression vector and stably transfected it into two human hepatoma cell lines, Huh7 and HepG2. Twenty-six Huh7 and two HepG2-positive clones were obtained after preliminary screening. Two Huh7 (SH-7 and -9) and one HepG2 (G-19) clones were chosen for further characterisation. Expression of HCV proteins in these cells accumulated from 6 In to 4 days posttreatment. Full-length viral plus-strand RNA was detected by Northern analyses. Using RT-PCR and ribonuclease protection assay, we also detected the synthesis of minus-strand HCV RNA. Plus- and minus-strand viral RNA was still detected after treatment with actinomycin D. Indirect immunofluorescence staining with anti-E2, NS4B, and NS5A revealed that these proteins were mostly localised to the endoplasmic reticulum (ER). Culture media from tet-induced SH-9 cells was separated on sucrose density gradients and analysed for the presence of HCV RNA. Viral RNA levels peaked at two separate ranges, one with a buoyant density of 1.08 g/ml and another from 1.17 to 1.39 g/ml. Electron microscopy demonstrated the presence of subviral-like particles (approximately 20-25 nm in diameter) in the cytoplasm of SH-9 and G-19 cells, which were positively labelled by anti-HCV core antibodies. Anti-E2 antibodies strongly labelled cytoplasmic vesicular structures and some viral-like particles. Complete viral particles of about 50 nm which reacted with anti-E2 antibodies were observed in the culture media of tet-induced SH-9 cells following negative staining. Supernatant from tet-treated SH-9 cells was found to infect naive Huh7 and stable Huh7-human CD81 cells. (C) 2002 Elsevier Science (USA).

The role of the Eph-ephrin signalling system in the regulation of developmental patterning

The Eph and ephrin system, consisting of fourteen Eph receptor tyrosine kinase proteins and nine ephrin membrane proteins in vertebrates, has been implicated in the regulation of many critical events during development. Binding of cell surface Eph and ephrin proteins results in bi-directional signals, which regulate the cytoskeletal, adhesive and motile properties of the interacting cells. Through these signals Eph and ephrin proteins are involved in early embryonic cell movements, which establish the germ layers, cell movements involved in formation of tissue boundaries and the pathfinding of axons. This review focuses on two vertebrate models, the zebrafish and mouse, in which experimental perturbation of Eph and/or ephrin expression in vivo have provided important insights into the role and functioning of the Eph/ephrin system.

Influence of nano-structure on electrolytic properties in CeO2 based system

Doped ceria (CeO2) compounds are fluorite type oxides that show oxygen ionic conductivity higher than yttria stabilized zirconia, in oxidizing atmosphere. In order to improve the conductivity, the effective index was suggested to maximize the oxygen ionic conductivity in doped CeO2 based oxides. In addition, the true microstructure of doped CeO2 was observed at atomic scale for conclusion of conduction mechanism. Doped CeO2 had small domains (10-50 nm) with ordered structure in a grain. It is found that the electrolytic properties strongly depended on the nano-structural feature at atomic scale in doped CeO2 electrolyte.

Expert system application on preliminary design of water retaining structures

Design of liquid retaining structures involves many decisions to be made by the designer based on rules of thumb, heuristics, judgment, code of practice and previous experience. Various design parameters to be chosen include configuration, material, loading, etc. A novice engineer may face many difficulties in the design process. Recent developments in artificial intelligence and emerging field of knowledge-based system (KBS) have made widespread applications in different fields. However, no attempt has been made to apply this intelligent system to the design of liquid retaining structures. The objective of this study is, thus, to develop a KBS that has the ability to assist engineers in the preliminary design of liquid retaining structures. Moreover, it can provide expert advice to the user in selection of design criteria, design parameters and optimum configuration based on minimum cost. The development of a prototype KBS for the design of liquid retaining structures (LIQUID), using blackboard architecture with hybrid knowledge representation techniques including production rule system and object-oriented approach, is presented in this paper. An expert system shell, Visual Rule Studio, is employed to facilitate the development of this prototype system. (C) 2002 Elsevier Science Ltd. All rights reserved.

Prediction of absolute rate coefficients and product branching ratios for the C(P-3) plus allene reaction system

Complex chemical reactions in the gas phase can be decomposed into a network of elementary (e.g., unimolecular and bimolecular) steps which may involve multiple reactant channels, multiple intermediates, and multiple products. The modeling of such reactions involves describing the molecular species and their transformation by reaction at a detailed level. Here we focus on a detailed modeling of the C(P-3)+allene (C3H4) reaction, for which molecular beam experiments and theoretical calculations have previously been performed. In our previous calculations, product branching ratios for a nonrotating isomerizing unimolecular system were predicted. We extend the previous calculations to predict absolute unimolecular rate coefficients and branching ratios using microcanonical variational transition state theory (mu-VTST) with full energy and angular momentum resolution. Our calculation of the initial capture rate is facilitated by systematic ab initio potential energy surface calculations that describe the interaction potential between carbon and allene as a function of the angle of attack. Furthermore, the chemical kinetic scheme is enhanced to explicitly treat the entrance channels in terms of a predicted overall input flux and also to allow for the possibility of redissociation via the entrance channels. Thus, the computation of total bimolecular reaction rates and partial capture rates is now possible. (C) 2002 American Institute of Physics.

A system for the heterologous expression of complex redox proteins in Rhodobacter capsulatus: characterisation of recombinant sulphite : cytochrome c oxidoreductase from Starkeya novella

The phototrophic purple non-sulfur bacterium Rhodobacter capsulatus expresses a wide variety of complex redox proteins in response to changing environmental conditions. Here we report the construction and evaluation of an expression system for recombinant proteins in that organism which makes use of the dor promoter from the same organism. A generic expression vector, pDorEX, was constructed and used to express sulphite:cytochrome c oxidoreductase from Starkeya novella, a heterodimeric protein containing both molybdenum and haem c. The recombinant protein was secreted to the periplasm and its biochemical properties were very similar to those of the native enzyme. The pDorEX system therefore seems to be potentially useful for heterologous expression of multi-subunit proteins containing complex redox cofactors. (C) 2002 Federation of European Biochemical Societies. Published by Elsevier Science B.V. All rights reserved.