Showing papers by "Brunel University London published in 1996"

Estrogenic activity of surfactants and some of their degradation products assessed using a recombinant yeast screen

Abstract: An estrogen-inducible screen was developed in yeast (Saccharomyces cerevisiae) in order to assess whether surfactants and their major degradation products are estrogenic. The DNA sequence of the human estrogen receptor (hER) was integrated into the yeast genome, which also contained expression plasmids carrying estrogen-responsive sequences (ERE) controlling the expression of the reporter gene lac-Z (encoding the enzyme β-galactosidase). Thus, in the presence of estrogens, β-galactosidase is synthesized and secreted into the medium, where it causes a color change from yellow to red. This recombinant strain was used to determine whether representatives of major surfactant classes and some of their principal degradation products possess estrogenic activity. The results were compared to the effects of the main natural estrogen 17β-estradiol. None of the parent surfactants tested possessed estrogenic activity. However, one class of surfactants, the alkylphenol polyethoxylates, degrade to persistent metabolites that were weakly estrogenic. Another group of degradation products, the sulfophenyl carboxylates, which are derived from the biodegradation of linear alkylbenzene sulfonates, do not appear to possess estrogenic activity.

Misunderstanding science? : the public reconstruction of science and technology

Abstract: Introduction Alan Irwin and Brian Wynne 1. Misunderstood misunderstandings: social identities and the public uptake of science Brian Wynne 2. Science and hell's kitchen: the local understanding of hazard issues Alan Irwin, Alison Dale and Denis Smith 3. Authorising science: public understanding of science in museums Sharon Macdonald 4. Disembodied knowledge? Making sense of medical science Helen Lambert and Hilary Rose 5. Now you see it, now you don't: mediating science and managing uncertainty in reproductive medicine Frances Price 6. Knowing ignorance and ignoring knowledge: discourses of ignorance in the public understanding of science Mike Michael 7. Insiders and outsiders: identifying experts on home ground Rosemary McKechnie 8. Nature's advocates: on putting science to work in environmental organisations Steven Yearley.

Inhibition of testicular growth in rainbow trout (Oncorhynchus mykiss) exposed to estrogenic alkylphenolic chemicals

Abstract: It is becoming evident that an increasing number of widely used industrial and agricultural chemicals are estrogenic. The biodegradation products of a major group of nonionic surfactants, the alkylphenol polyethoxylates, are one such group. Some of these chemicals are widespread aquatic pollutants, and bioconcentrate in aquatic biota. Exposure of male rainbow trout (Oncorhynchus mykiss) to four different alkylphenolic chemicals caused synthesis of vitellogenin, a process normally dependent on endogenous estrogens, and a concomitant inhibition of testicular growth. The magnitude of these estrogenic effects was dependent on the estrogenic potency of the chemical, the stage of reproductive development of the fish, and the concentration of the chemical in the water. These results support the contention that exposure of wildlife to environmentally persistent estrogenic chemicals can result in deleterious reproductive consequences.

Oocyte growth and development in teleosts

Abstract: Oocyte growth and development is an important issue in fish and fisheries biology. This paper reviews the information available on oocyte growth patterns and the rates and dynamics of oocyte growth in teleosts. In synchronous spawners, the weight of the gonad may represent as much as 40% of the overall body weight of the fish. In asynchronous spawners, the weight of the mature ovary is considerably less than in synchronous ovulators, but the ovary shows a more regular periodicity and may grow repeatedly many times during the breeding season. There is a huge variability in egg size in teleosts, with the largest known measuring up to 8 cm in diameter. Within the limits of variance set by genetic constraints, egg size may vary between populations of the same species. Oocytes in all teleosts undergo the same basic pattern of growth: oogenesis, primary oocyte growth, cortical alveolus stage, vitellogenesis, maturation and ovulation. The mechanisms that control oocyte growth are addressed in this review, albeit that the available information, as in all other vertebrates, is very limited. The main hormones that have been shown to affect ovarian growth are gonadotrophin, thyroid hormones, growth hormone, insulin and insulin-like growth factors. An overview of the determinants of fecundity, with particular reference to oocyte recruitment and atresia, is the focus of the second part of the paper. Genetics and nutrition have major effects on fecundity, and studies so far suggest that the determinants of fecundity usually operate during the early part of gametogenesis. The role of atresia in determining fecundity is less clear. The final part of this review highlights some areas of study that are priorities for research on ovarian development in fish.

A survey of estrogenic activity in United Kingdom inland waters

Abstract: Vitellogenin, a yolk-precursor protein normally found only in the blood plasma of sexually mature female teleosts and other egg-laying vertebrates, was used as an indicator of exposure of male rainbow trout (Oncorhynchus mykiss) to exogenous estrogens. Vitellogenin concentrations were measured using a specific radioimmunoassay for trout. Cages containing adult male trout were placed at the points of discharge and at varying distances downstream of treated sewage effluent outfalls into the River Lea (UK) during the summer and winter months of 1992. After 3 weeks exposure at the majority of sites, fish held up to 15 km downstream of inputs showed an increase in plasma vitellogenin concentration, with statistically significant elevations up to 4.5 km downstream. A repeat survey in November 1992 below Harpenden sewage treatment works showed that the only two stations to give a significant response were 3 m and 1.6 km downstream of the outfall. This reduced effect compared to the first survey is thought to be due to dilution of both the influent sewage to the treatment works and of the river water itself by increased rainfall, the overall increase in dilution being approx. 36%. Trout were also placed in 15 raw water storage reservoirs in southeast England during the summer of 1993 for an exposure period of 6 weeks. No biologically significant increases in plasma vitellogenin concentration were observed in any of the reservoirs.

How can payback from health services research be assessed

Abstract: Throughout the world there is a growing recognition that health care should be research-led. This strengthens the requirement for expenditure on health services research to be justified by demonstrating the benefits it produces. However, payback from health research and development is a complex concept and little used term. Five main categories of payback can be identified: knowledge; research benefits; political and administrative benefits; health sector benefits; and broader economic benefits. Various models of research utilization together with previous assessments of payback from research helped in the development of a new conceptual model of how and where payback may occur. The model combines an input-output perspective with an examination of the permeable interfaces between research and its environment. The model characterizes research projects in terms of Inputs, Processes, and Primary Outputs. The last consist of knowledge and research benefits. There are two interfaces between the project and its environment. The first (Project Specification, Selection and Commissioning) is the link with Research Needs Assessment. The second (Dissemination) should lead to Secondary Outputs (which are policy or administrative decisions), and usually Applications (which take the form of behavioural changes), from which Impacts or Final Outcomes result. It is at this final stage that health and wider economic benefits can be measured. A series of case studies were used to assess the feasibility both of applying the model and the payback categorization. The paper draws various conclusions from the case studies and identifies a range of issues for further work.

Validation of radioimmunoassays for two salmon gonadotropins (GTH I and GTH II) and their plasma concentrations throughout the reproductivecycle in male and female rainbow trout (Oncorhynchus mykiss).

Abstract: RIAs were developed for the two salmon gonadotropins (GTH I and GTH II) and used to measure plasma GTH throughout the life of the rainbow trout, Oncorhynchus mykiss. The RIA for GTH II was specific and sensitive (< 0.001% cross-reaction with GTH I, mean sensitivity = 0.26 0.02 ng/ml). The RIA for GTH I was less specific and less sensitive than the GTH II RIA (9.7% cross-reaction with GTH II, mean sensitivity = 2.34 ± 0.23 ng/ml). In both males and females, the levels of GTH II remained undetectable (< 0.3 ng/ml) throughout most of the reproductive cycle, until shortly preceding spermiation/ovulation, when they began to rise. Concentrations of plasma GTH II were maximal at spermiation/ovulation. In both sexes, plasma profiles of GTH I differed from those of GTH II. The plasma GTH I concentration in females was elevated during early vitellogenesis. It then fell to a basal level shortly before ovulation and finally was elevated again at ovulation. In males, increases in plasma GTH I were seen a year before spermiation and again later, during the final stages of testicular growth. These results support the contention that GTH I mediates gonadal growth, whereas GTH II regulates the final stages of maturation and ovulation/spermiation. In rainbow trout, plasma profiles of GTH I and GTH II mimic the cycles of plasma FSH and LH, respectively, in the ovulatory cycle of higher vertebrates.

Hypersensitivity to very-low single radiation doses: Its relationship to the adaptive response and induced radioresistance

Abstract: There is now little doubt of the existence of radioprotective mechanisms, or stress responses, that are upregulated in response to exposure to small doses of ionizing radiation and other DNA-damaging agents. Phenomenologically, there are two ways in which these induced mechanisms operate. First, a small conditioning dose (generally below 30 cGy) may protect against a subsequent, separate, exposure to radiation that may be substantially larger than the initial dose. This has been termed the adaptive response. Second, the response to single doses may itself be dose-dependent so that small acute radiation exposures, or exposures at very low dose rates, are more effective per unit dose than larger exposures above the threshold where the induced radioprotection is triggered. This combination has been termed low-dose hypersensitivity (HRS) and induced radioresistance (IRR) as the dose increases. Both the adaptive response and HRS/IRR have been well documented in studies with yeast, bacteria, protozoa, algae, higher plant cells, insect cells, mammalian and human cells in vitro, and in studies on animal models in vivo. There is indirect evidence that the HRS/IRR phenomenon in response to single doses is a manifestation of the same underlying mechanism that determines the adaptive response in the two-dose case and that it can be triggered by high and low LET radiations as well as a variety of other stress-inducing agents such as hydrogen peroxide and chemotherapeutic agents although exact homology remains to be tested. Little is currently known about the precise nature of this underlying mechanism, but there is evidence that it operates by increasing the amount and rate of DNA repair, rather than by indirect mechanisms such as modulation of cell-cycle progression or apoptosis. Changed expression of some genes, only in response to low and not high doses, may occur within a few hours of irradiation and this would be rapid enough to explain the phenomenon of induced radioresistance although its specific molecular components have yet to be identified.

Measurement of vitellogenin, a biomarker for exposure to oestrogenic chemicals, in a wide variety of cyprinid fish

Abstract: There is increasing concern about man-made chemicals in the aquatic environment that mimic oestrogens because they may disrupt reproductive function. Vitellogenin, a precursor of egg-yolk in fish and other oviparous animals, may be used as a biomarker for “oestrogen” exposure. This study investigated the use of a radioimmunoassay developed to carp (Cyprinus carpio) vitellogenin to measure vitellogenin in other species of fish, especially cyprinids that would be of value for field and laboratory studies on oestrogenic xenobiotics. Of the nine families of fish studied, only vitellogenin from cyprinids (to which the carp belongs) showed good cross-reactivity in the carp vitellogenin radioimmunoassay. Vitellogenin from cyprinids native to Europe that cross reacted in the carp vitellogenin radioimmunoassay included: bream (Abramis brama), roach (Rutilus rutilus), rudd (Scardinius erythropthalmus), gudgeon (Gobio gobio) and minnow (Phoxinus phoxinus). Vitellogenin from cyprinids used widely in ecotoxicology that cross reacted in the carp vitellogenin radioimmunoassay included: fathead minnow (Pimephales promelas), zebrafish (Brachydanio rerio) and goldfish (Carassius auratus). In the cyprinids studies, the concentrations of vitellogenin in mature females were between a few hundred and a thousand microgram per millilitre. Concentrations of plasma vitellogenin in immature females were always greater than 200 ng·m-1, whereas in males (with the exception of the fathead minnow) plasma vitellogenin concentrations were less than 20 ng·ml-1 (and generally, much lower). The results suggest that the structure of vitellogenin is highly conserved within the cyprinid family and that the carp vitellogenin radioimmunoassay may be used to measure the concentrations of vitellogenin in plasma from a wide variety of cyprinids.

Economic dispatch of generators with prohibited operating zones: a genetic algorithm approach

Abstract: The work explores the use of a genetic algorithm for the solution of an economic dispatch problem in power systems where some of the units have prohibited operating zones. Genetic algorithms have a capability to provide global optimal solutions in problem domains where a complete traversion of the whole search space is computationally infeasible. Two different implementations of the genetic algorithm for the solution of this dispatch problem are presented: a standard genetic algorithm, and a deterministic crowding genetic algorithm model. The results demonstrate that the genetic algorithm can be applied successfully in the solution of problems represented with nonconvex functions.

The Dilution, Chemical, and Thermal Effects of Exhaust Gas Recirculation on Diesel Engine Emissions - Part 1: Effect of Reducing Inlet Charge Oxygen

Abstract: This is a first of a series of papers describing how the replacement of some of the inlet air with EGR modifies the diesel combustion process and thereby affects the exhaust emissions This paper deals with only the reduction of oxygen in the inlet charge to the engine (dilution effect) The oxygen in the inlet charge to a direct injection diesel engine was progressively replaced by inert gases, whilst the engine speed, fuelling rate, injection timing, total mass and the specific heat capacity of the inlet charge were kept constant The use of inert gases for oxygen replacement, rather than carbon dioxide (CO 2) or water vapour normally found in EGR, ensured that the effects on combustion of dissociation of these species were excluded In addition, the effects of oxygen replacement on ignition delay were isolated and quantified Results from final set of tests are also presented during which the inlet charge temperature was raised progressively to quantify the effect that EGR temperature has on combustion and emissions The reduction in the inlet charge oxygen (dilution effect) resulted in very large reductions in exhaust NO x level at the expense of rises in particulates and unburnt hydrocarbon emissions The engine power output and fuel economy also deteriorated substantially Raising the inlet charge temperature increases NOx but also, substantially, the exhaust smoke and particulate emissions © 1996 Society of Automotive Engineers, Inc

Power in Discourse: The Case of Arguments on a British Talk Radio Show

Abstract: This article presents an approach to exploring the ways in which power functions in institutional discourse. The principal aim of the article is to show how the play of power in discourse can be analysed from the fundamentally local, sequential perspective of conversation analysis. I argue that power is best seen as a shifting distribution of resources which enable some participants locally to achieve interactional effects not available to others. Using calls to a British talk radio show as a case study, I show how these resources are linked to the interactional and technological organization of participation in the setting.

Road traffic offending, stress, age, and accident history among male and female drivers

Abstract: This paper draws on data gathered during a larger study of driving behaviour to explore possible connections between stress, offending against the traffic laws, and accident rates, and gives particular attention to comparisons between male and female drivers. Data were gathered from 422 drivers by a postal questionnaire, and further measures of stress were obtained during semi-structured interviews with a specially selected subset of 66 of them. Analyses of variance investigated links between offending rates, accident history, and up to seven measures of stress, taking age and gender into account. In the results accident history, although positively related to offending, played little part in links involving stress variables. The principal findings were that (a) stress, both on and off the road, was positively associated with offending among both male and female drivers, and (b) although females overall offended less than males, females experienced more stress than males whatever their level of offending. One possible interpretation of these results is suggested by the feminist literature, which could account for both the higher levels of stress and lower levels of offending found among women drivers. However, there is unlikely to be a clear-cut gender divide in offending-stress relationships, and some small groups of female drivers in the study behaved like male ones. It is suggested that people's driving reflects their lifestyles, and that women drivers' patterns of offending and stress will resemble those of male drivers to the extent that their lives and concerns are similar to men's. It is concluded that this position warrants further research.

Mammography screening : an incremental cost effectiveness analysis of double versus single reading of mammograms

Abstract: Objective: To compare mammography reading by one radiologist with independent reading by two radiologists. Design: An observational non-randomised trial at St Margaret9s Hospital, Epping. Subjects: 33734 consecutive attenders for breast screening in the main trial and a sample of 132 attenders for assessment who provided data on private costs. Interventions: Three reporting policies were compared: single reading, consensus double reading, and non-consensus double reading. Main outcome measures: Numbers of cancers detected, recall rates, screening and assessment costs, and cost effectiveness ratios. Results: A policy of double reading followed by consensus detected an additional nine cancers per 10000 women screened (95% confidence interval 5 to 13) compared with single reading. A non-consensus double reading policy detected an additional 10 cancers per 10000 women screened (95% confidence interval 6 to 14). The difference in numbers of cancers detected between the consensus and non-consensus double reading policies was not significant (95% confidence interval -0.2 to 2.2). The proportion of women recalled for assessment after consensus double reading was significantly lower than after single reading (difference 2.7%; 95% confidence interval 2.4% to 3.0%). The recall rate with the non-consensus policy was significantly higher than with single reading (difference 3.0%; 2.5% to 3.5%). Consensus double reading cost less than single reading (saving pounds sterling4853 per 10000 women screened). Non-consensus double reading cost more than single reading (difference pounds sterling19259 per 10000 women screened). Conclusions: In the screening unit studied a consensus double reading policy was more effective and less costly than a single reading policy. Key messages Key messages Double reading of screening mammograms detects more cancers than does single reading Double reading with consensus reduces recall rates and has a lower total cost than single reading Breast screening units should consider adopting consensus double reporting for the first screening examination in order to improve efficiency Double reading with consensus is also likely to confer benefits at subsequent screening examinations, though the magnitude and cost effectiveness of these benefits are not known

Cost effectiveness of screening for and eradication of Helicobacter pylori in management of dyspeptic patients under 45 years of age.

Abstract: Objective: To assess the cost effectiveness of screening for and eradicating Helicobacter pylori in patients under 45 years of age presenting with dyspepsia. Design: A decision analytic model composed of a decision tree to represent the epidemiology of dyspepsia and a Markov process to model the outcomes of treatment. Patients: Patients under the age of 45 years presenting to their general practitioner with (peptic type) dyspepsia. Interventions: Conventional empirical treatment with healing and maintenance doses of cimetidine v eradication treatment solely in patients with confirmed peptic ulcer; and conventional empirical treatment for all dyspeptic patients compared with the use of a serology test to identify patients with H pylori, who then receive endoscopy to investigate the presence of peptic ulcer disease and, when disease is found, are given eradication treatment with a breath test to confirm successful eradication. Main outcome measures: Expected cumulative costs over a period of 10 years. The proportion of time patients spend without a recurrent ulcer. Results: After receiving eradication treatment, patients with confirmed ulcer spend an average of 99% of their time free from recurrent ulcer disease compared with 95% after treatment with cimetidine. Eradication treatment costs less than that with cimetidine. When the initial cost of identifying appropriate patients to receive eradication treatment is added to the analysis, however, these cost savings take almost eight years to accrue. Conclusions: Enthusiasm for introducing testing for and eradication of H pylori for dyspeptic patients in general practice should be tempered by an awareness that cost savings may take many years to realise. Key messages Patients under the age of 45 years presenting with peptic-type dyspepsia without sinister symp- toms are usually managed empirically Only a minority of these patients will have peptic ulcer disease and Helicobacter pylori infection Identification of appropriate patients for H pylori eradication treatment from among dyspeptic patients will entail a considerable investment of resources Consequently, the cost savings associated with a reduction in use of H2 antagonists by patients who receive successful H pylori eradication may take many years to materialise

Connectivity analysis: a tool for processing geometric constraints

Abstract: The use of geometric constraints allows computer-aided design systems to capture a designer's intent. This paper describes algorithms to process geometric constraints, including numerical relationships between dimension values. The proposed algorithms analyse the connectivity between constraints and the geometric entities which they constrain. One algorithm identifies parts of a geometric configuration that are subject to too many or too few constraints, and describes all possible options for correcting such potential problems. Another uses constraint priorities to select from those options. The final algorithm subdivides a large set of constraints into small subsets that can be resolved independently.

The arbitrage pricing theory, macroeconomic and financial factors, and expectations generating processes

Abstract: Empirical tests of the arbitrage pricing theory (APT) using prespecified observed variables rely on the construction of unexpected components of the variables. In this paper we show that traditional techniques employed in this area may lead to false inferences regarding the statistical significance or otherwise of estimated risk premia. We put forth an alternative methodology to generate the unexpected components which treats expectations formation as a learning process. In the light of given criteria that the unexpected components should satisfy this technique leads to more reliable inferences regarding tests and applications of the APT.

An analysis of the scope and value of problem-based learning in the education of health care professionals.

Abstract: Whilst on teaching practice at an institute of higher education, I became increasingly aware of the limitations of subject-based, teacher-centred courses in the education of health care professionals My involvement in problem-based learning indicated the possibility of this innovative form of education bridging the gap between theory and practice This investigation reveals the dissatisfaction of some educationalists with traditional training courses and the spread world wide of problem-based learning as an alternative method of developing curriculum The process of using problem-based learning in the classroom is discussed and its strengths and weaknesses analysed for both teachers and students This article suggests that problem-based learning is more likely to equip health care professionals to deal with the demands of a changing society than conventional courses

Measures of effect size.

Abstract: Two different approaches have been used to derive measures of effect size. One approach is based on the comparison of treatment means. The standardized mean difference is an appropriate measure of effect size when one is merely comparing two treatments, but there is no satisfactory analogue for comparing more than two treatments. The second approach is based on the proportion of variance in the dependent variable that is explained by the independent variable. Estimates have been proposed for both fixed-factor and random-factor designs, but their sampling properties are not well understood. Nevertheless, measures of effect size can allow quantitative comparisons to be made across different studies, and they can be a useful adjunct to more traditional outcome measures such as test statistics and significance levels.